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tgarc/MultiIndex

Last active August 29, 2015 14:24
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MultiIndex
{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# A short tutorial on pandas MultiIndexing with DataFrames"
]
},
{
"cell_type": "code",
"execution_count": 1,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"pandas version: 0.16.2\n"
]
}
],
"source": [
"import pandas as pd\n",
"import numpy as np\n",
"from IPython.display import display\n",
"\n",
"print \"pandas version:\",pd.version.version"
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
"<div>\n",
"<table border=\"1\" class=\"dataframe\">\n",
" <thead>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl1</th>\n",
" <th colspan=\"4\" halign=\"left\">x1</th>\n",
" <th colspan=\"4\" halign=\"left\">x2</th>\n",
" <th colspan=\"4\" halign=\"left\">x3</th>\n",
" <th colspan=\"4\" halign=\"left\">x4</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl3</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>rlvl1</th>\n",
" <th>rlvl2</th>\n",
" <th>rlvl3</th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <th rowspan=\"4\" valign=\"top\">a1</th>\n",
" <th rowspan=\"2\" valign=\"top\">b1</th>\n",
" <th>c1</th>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>2</td>\n",
" <td>3</td>\n",
" <td>5</td>\n",
" </tr>\n",
" <tr>\n",
" <th>c2</th>\n",
" <td>3</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" <td>5</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>2</td>\n",
" <td>9</td>\n",
" <td>8</td>\n",
" <td>1</td>\n",
" <td>8</td>\n",
" <td>7</td>\n",
" <td>0</td>\n",
" <td>6</td>\n",
" <td>0</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">b2</th>\n",
" <th>c1</th>\n",
" <td>4</td>\n",
" <td>0</td>\n",
" <td>5</td>\n",
" <td>7</td>\n",
" <td>0</td>\n",
" <td>4</td>\n",
" <td>8</td>\n",
" <td>5</td>\n",
" <td>7</td>\n",
" <td>1</td>\n",
" <td>9</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" </tr>\n",
" <tr>\n",
" <th>c2</th>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>8</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
" <td>4</td>\n",
" <td>4</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>1</td>\n",
" <td>8</td>\n",
" <td>0</td>\n",
" <td>6</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"4\" valign=\"top\">a2</th>\n",
" <th rowspan=\"2\" valign=\"top\">b1</th>\n",
" <th>c1</th>\n",
" <td>3</td>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>2</td>\n",
" <td>8</td>\n",
" <td>5</td>\n",
" <td>7</td>\n",
" <td>0</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>2</td>\n",
" <td>5</td>\n",
" <td>1</td>\n",
" <td>4</td>\n",
" </tr>\n",
" <tr>\n",
" <th>c2</th>\n",
" <td>6</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>9</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" <td>1</td>\n",
" <td>2</td>\n",
" <td>3</td>\n",
" <td>5</td>\n",
" <td>9</td>\n",
" <td>8</td>\n",
" <td>3</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">b2</th>\n",
" <th>c1</th>\n",
" <td>8</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>7</td>\n",
" <td>9</td>\n",
" <td>8</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>6</td>\n",
" <td>1</td>\n",
" <td>8</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" <td>9</td>\n",
" </tr>\n",
" <tr>\n",
" <th>c2</th>\n",
" <td>7</td>\n",
" <td>4</td>\n",
" <td>9</td>\n",
" <td>7</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>3</td>\n",
" <td>8</td>\n",
" <td>4</td>\n",
" <td>5</td>\n",
" <td>3</td>\n",
" <td>1</td>\n",
" <td>9</td>\n",
" <td>4</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"4\" valign=\"top\">a3</th>\n",
" <th rowspan=\"2\" valign=\"top\">b1</th>\n",
" <th>c1</th>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>8</td>\n",
" <td>0</td>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>2</td>\n",
" <td>7</td>\n",
" <td>8</td>\n",
" <td>4</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>2</td>\n",
" <td>1</td>\n",
" <td>7</td>\n",
" </tr>\n",
" <tr>\n",
" <th>c2</th>\n",
" <td>4</td>\n",
" <td>9</td>\n",
" <td>5</td>\n",
" <td>2</td>\n",
" <td>1</td>\n",
" <td>2</td>\n",
" <td>3</td>\n",
" <td>2</td>\n",
" <td>7</td>\n",
" <td>8</td>\n",
" <td>9</td>\n",
" <td>6</td>\n",
" <td>5</td>\n",
" <td>5</td>\n",
" <td>9</td>\n",
" <td>1</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">b2</th>\n",
" <th>c1</th>\n",
" <td>6</td>\n",
" <td>8</td>\n",
" <td>9</td>\n",
" <td>9</td>\n",
" <td>6</td>\n",
" <td>0</td>\n",
" <td>1</td>\n",
" <td>2</td>\n",
" <td>2</td>\n",
" <td>9</td>\n",
" <td>9</td>\n",
" <td>3</td>\n",
" <td>0</td>\n",
" <td>5</td>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" </tr>\n",
" <tr>\n",
" <th>c2</th>\n",
" <td>9</td>\n",
" <td>8</td>\n",
" <td>4</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" <td>3</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>7</td>\n",
" <td>0</td>\n",
" <td>8</td>\n",
" <td>8</td>\n",
" <td>0</td>\n",
" <td>4</td>\n",
" <td>2</td>\n",
" <td>9</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"4\" valign=\"top\">a4</th>\n",
" <th rowspan=\"2\" valign=\"top\">b1</th>\n",
" <th>c1</th>\n",
" <td>7</td>\n",
" <td>1</td>\n",
" <td>6</td>\n",
" <td>1</td>\n",
" <td>7</td>\n",
" <td>2</td>\n",
" <td>6</td>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
" <td>3</td>\n",
" <td>2</td>\n",
" <td>9</td>\n",
" <td>4</td>\n",
" <td>0</td>\n",
" <td>2</td>\n",
" </tr>\n",
" <tr>\n",
" <th>c2</th>\n",
" <td>8</td>\n",
" <td>2</td>\n",
" <td>7</td>\n",
" <td>9</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
" <td>8</td>\n",
" <td>2</td>\n",
" <td>2</td>\n",
" <td>0</td>\n",
" <td>9</td>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>6</td>\n",
" <td>4</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">b2</th>\n",
" <th>c1</th>\n",
" <td>9</td>\n",
" <td>3</td>\n",
" <td>8</td>\n",
" <td>6</td>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>8</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>4</td>\n",
" <td>1</td>\n",
" <td>5</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>3</td>\n",
" </tr>\n",
" <tr>\n",
" <th>c2</th>\n",
" <td>8</td>\n",
" <td>9</td>\n",
" <td>9</td>\n",
" <td>5</td>\n",
" <td>6</td>\n",
" <td>1</td>\n",
" <td>5</td>\n",
" <td>7</td>\n",
" <td>9</td>\n",
" <td>2</td>\n",
" <td>9</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>1</td>\n",
" <td>2</td>\n",
" <td>8</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"text/plain": [
"clvl1 x1 x2 x3 x4 \n",
"clvl2 y1 y2 y1 y2 y1 y2 y1 y2 \n",
"clvl3 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2\n",
"rlvl1 rlvl2 rlvl3 \n",
"a1 b1 c1 2 4 3 7 5 3 6 9 0 5 8 3 6 2 3 5\n",
" c2 3 4 6 6 5 6 3 2 9 8 1 8 7 0 6 0\n",
" b2 c1 4 0 5 7 0 4 8 5 7 1 9 4 7 6 6 6\n",
" c2 7 5 8 8 4 7 4 4 9 0 3 6 1 8 0 6\n",
"a2 b1 c1 3 2 4 2 8 5 7 0 4 6 3 7 2 5 1 4\n",
" c2 6 4 6 3 9 3 6 0 3 1 2 3 5 9 8 3\n",
" b2 c1 8 9 0 7 9 8 0 3 7 6 1 8 9 0 3 9\n",
" c2 7 4 9 7 3 7 3 8 4 5 3 1 9 4 0 3\n",
"a3 b1 c1 9 0 8 0 7 5 8 2 7 8 4 3 7 2 1 7\n",
" c2 4 9 5 2 1 2 3 2 7 8 9 6 5 5 9 1\n",
" b2 c1 6 8 9 9 6 0 1 2 2 9 9 3 0 5 2 4\n",
" c2 9 8 4 0 3 3 9 0 7 0 8 8 0 4 2 9\n",
"a4 b1 c1 7 1 6 1 7 2 6 2 4 7 3 2 9 4 0 2\n",
" c2 8 2 7 9 4 7 8 2 2 0 9 7 5 8 6 4\n",
" b2 c1 9 3 8 6 2 4 8 5 8 4 1 5 4 6 3 3\n",
" c2 8 9 9 5 6 1 5 7 9 2 9 5 8 1 2 8"
]
},
"metadata": {},
"output_type": "display_data"
}
],
"source": [
"midx_col = pd.MultiIndex.from_product([['x1', 'x2', 'x3', 'x4'], ['y1', 'y2'],['z1','z2']],names=['clvl1','clvl2','clvl3'])\n",
"midx_row = pd.MultiIndex.from_product([['a1', 'a2', 'a3', 'a4'], ['b1', 'b2'],['c1','c2']],names=['rlvl1','rlvl2','rlvl3'])\n",
"df = pd.DataFrame(np.random.randint(10,size=(16,16)),index=midx_row,columns=midx_col)\n",
"\n",
"display(df)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Single indexing on a MultiIndexed Dataframe"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Indexing the first *l < L* levels (where *L* = `len(MultiIndex.levels)`) returns a `DataFrame` with the first *l* levels of the row index dropped.\n",
"\n",
"If *l == L* a `Series` is returned.\n",
"\n",
"Note that the column index is always kept intact."
]
},
{
"cell_type": "code",
"execution_count": 3,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
"<div>\n",
"<table border=\"1\" class=\"dataframe\">\n",
" <thead>\n",
" <tr>\n",
" <th>clvl1</th>\n",
" <th colspan=\"4\" halign=\"left\">x1</th>\n",
" <th colspan=\"4\" halign=\"left\">x2</th>\n",
" <th colspan=\"4\" halign=\"left\">x3</th>\n",
" <th colspan=\"4\" halign=\"left\">x4</th>\n",
" </tr>\n",
" <tr>\n",
" <th>clvl2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>clvl3</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>rlvl3</th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <th>c1</th>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>2</td>\n",
" <td>3</td>\n",
" <td>5</td>\n",
" </tr>\n",
" <tr>\n",
" <th>c2</th>\n",
" <td>3</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" <td>5</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>2</td>\n",
" <td>9</td>\n",
" <td>8</td>\n",
" <td>1</td>\n",
" <td>8</td>\n",
" <td>7</td>\n",
" <td>0</td>\n",
" <td>6</td>\n",
" <td>0</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"text/plain": [
"clvl1 x1 x2 x3 x4 \n",
"clvl2 y1 y2 y1 y2 y1 y2 y1 y2 \n",
"clvl3 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2\n",
"rlvl3 \n",
"c1 2 4 3 7 5 3 6 9 0 5 8 3 6 2 3 5\n",
"c2 3 4 6 6 5 6 3 2 9 8 1 8 7 0 6 0"
]
},
"metadata": {},
"output_type": "display_data"
},
{
"data": {
"text/plain": [
"clvl1 clvl2 clvl3\n",
"x1 y1 z1 2\n",
" z2 4\n",
" y2 z1 3\n",
" z2 7\n",
"x2 y1 z1 5\n",
" z2 3\n",
" y2 z1 6\n",
" z2 9\n",
"x3 y1 z1 0\n",
" z2 5\n",
" y2 z1 8\n",
" z2 3\n",
"x4 y1 z1 6\n",
" z2 2\n",
" y2 z1 3\n",
" z2 5\n",
"Name: (a1, b1, c1), dtype: int64"
]
},
"metadata": {},
"output_type": "display_data"
}
],
"source": [
"display(df.loc['a1','b1'])\n",
"display(df.loc['a1','b1','c1'])"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"We can also select all indices at a particular level by using a colon `:`. Note that if we use a colon at any index level, the MultiIndex from the original DataFrame is kept intact (i.e. none of the levels are dropped)."
]
},
{
"cell_type": "code",
"execution_count": 4,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
"<div>\n",
"<table border=\"1\" class=\"dataframe\">\n",
" <thead>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl1</th>\n",
" <th colspan=\"4\" halign=\"left\">x1</th>\n",
" <th colspan=\"4\" halign=\"left\">x2</th>\n",
" <th colspan=\"4\" halign=\"left\">x3</th>\n",
" <th colspan=\"4\" halign=\"left\">x4</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl3</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>rlvl1</th>\n",
" <th>rlvl2</th>\n",
" <th>rlvl3</th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a1</th>\n",
" <th>b1</th>\n",
" <th>c1</th>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>2</td>\n",
" <td>3</td>\n",
" <td>5</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c1</th>\n",
" <td>4</td>\n",
" <td>0</td>\n",
" <td>5</td>\n",
" <td>7</td>\n",
" <td>0</td>\n",
" <td>4</td>\n",
" <td>8</td>\n",
" <td>5</td>\n",
" <td>7</td>\n",
" <td>1</td>\n",
" <td>9</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"text/plain": [
"clvl1 x1 x2 x3 x4 \n",
"clvl2 y1 y2 y1 y2 y1 y2 y1 y2 \n",
"clvl3 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2\n",
"rlvl1 rlvl2 rlvl3 \n",
"a1 b1 c1 2 4 3 7 5 3 6 9 0 5 8 3 6 2 3 5\n",
" b2 c1 4 0 5 7 0 4 8 5 7 1 9 4 7 6 6 6"
]
},
"execution_count": 4,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"df.loc['a1',:,'c1']"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Selecting arbitrary indices at multiple levels <a id=\"arbitrary_multi-indexing\"></a>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The previous examples showed how to select rows that match only a single index at each index level (actually we learned that we can also select all indices at a particular level by using colon `:`). But it's also possible to select arbitrary indices at each index level by using indexing of the form\n",
"\n",
"`df.loc[( (rlvl1 indices), (rlvl2 indices), (rlvl3 indices) ), ( (clvl1 indices), (clvl2 indices), (clvl3 indices) )]`\n",
"\n",
"Note that\n",
"\n",
"1. The column index must be explicitly set \n",
"2. The order of index tuples must match the order of index levels\n",
"\n",
"I'll go into more detail on this syntax in the [next](#ambiguities) section."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Here's a few examples"
]
},
{
"cell_type": "code",
"execution_count": 5,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
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"<div>\n",
"<table border=\"1\" class=\"dataframe\">\n",
" <thead>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl1</th>\n",
" <th colspan=\"4\" halign=\"left\">x1</th>\n",
" <th colspan=\"4\" halign=\"left\">x2</th>\n",
" <th colspan=\"4\" halign=\"left\">x3</th>\n",
" <th colspan=\"4\" halign=\"left\">x4</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl3</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
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" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>rlvl1</th>\n",
" <th>rlvl2</th>\n",
" <th>rlvl3</th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
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" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
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" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a1</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>3</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" <td>5</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>2</td>\n",
" <td>9</td>\n",
" <td>8</td>\n",
" <td>1</td>\n",
" <td>8</td>\n",
" <td>7</td>\n",
" <td>0</td>\n",
" <td>6</td>\n",
" <td>0</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>8</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
" <td>4</td>\n",
" <td>4</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>1</td>\n",
" <td>8</td>\n",
" <td>0</td>\n",
" <td>6</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a2</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>6</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>9</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" <td>1</td>\n",
" <td>2</td>\n",
" <td>3</td>\n",
" <td>5</td>\n",
" <td>9</td>\n",
" <td>8</td>\n",
" <td>3</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>7</td>\n",
" <td>4</td>\n",
" <td>9</td>\n",
" <td>7</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>3</td>\n",
" <td>8</td>\n",
" <td>4</td>\n",
" <td>5</td>\n",
" <td>3</td>\n",
" <td>1</td>\n",
" <td>9</td>\n",
" <td>4</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a4</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>8</td>\n",
" <td>2</td>\n",
" <td>7</td>\n",
" <td>9</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
" <td>8</td>\n",
" <td>2</td>\n",
" <td>2</td>\n",
" <td>0</td>\n",
" <td>9</td>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>6</td>\n",
" <td>4</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>8</td>\n",
" <td>9</td>\n",
" <td>9</td>\n",
" <td>5</td>\n",
" <td>6</td>\n",
" <td>1</td>\n",
" <td>5</td>\n",
" <td>7</td>\n",
" <td>9</td>\n",
" <td>2</td>\n",
" <td>9</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>1</td>\n",
" <td>2</td>\n",
" <td>8</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"text/plain": [
"clvl1 x1 x2 x3 x4 \n",
"clvl2 y1 y2 y1 y2 y1 y2 y1 y2 \n",
"clvl3 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2\n",
"rlvl1 rlvl2 rlvl3 \n",
"a1 b1 c2 3 4 6 6 5 6 3 2 9 8 1 8 7 0 6 0\n",
" b2 c2 7 5 8 8 4 7 4 4 9 0 3 6 1 8 0 6\n",
"a2 b1 c2 6 4 6 3 9 3 6 0 3 1 2 3 5 9 8 3\n",
" b2 c2 7 4 9 7 3 7 3 8 4 5 3 1 9 4 0 3\n",
"a4 b1 c2 8 2 7 9 4 7 8 2 2 0 9 7 5 8 6 4\n",
" b2 c2 8 9 9 5 6 1 5 7 9 2 9 5 8 1 2 8"
]
},
"metadata": {},
"output_type": "display_data"
},
{
"data": {
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"<div>\n",
"<table border=\"1\" class=\"dataframe\">\n",
" <thead>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl3</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>rlvl1</th>\n",
" <th>rlvl2</th>\n",
" <th>rlvl3</th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a1</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>3</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>8</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a2</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>6</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>7</td>\n",
" <td>4</td>\n",
" <td>9</td>\n",
" <td>7</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a4</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>8</td>\n",
" <td>2</td>\n",
" <td>7</td>\n",
" <td>9</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>8</td>\n",
" <td>9</td>\n",
" <td>9</td>\n",
" <td>5</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"text/plain": [
"clvl2 y1 y2 \n",
"clvl3 z1 z2 z1 z2\n",
"rlvl1 rlvl2 rlvl3 \n",
"a1 b1 c2 3 4 6 6\n",
" b2 c2 7 5 8 8\n",
"a2 b1 c2 6 4 6 3\n",
" b2 c2 7 4 9 7\n",
"a4 b1 c2 8 2 7 9\n",
" b2 c2 8 9 9 5"
]
},
"metadata": {},
"output_type": "display_data"
},
{
"data": {
"text/html": [
"<div>\n",
"<table border=\"1\" class=\"dataframe\">\n",
" <thead>\n",
" <tr style=\"text-align: right;\">\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl3</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>rlvl1</th>\n",
" <th>rlvl2</th>\n",
" <th>rlvl3</th>\n",
" <th></th>\n",
" <th></th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a1</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>3</td>\n",
" <td>4</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a2</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>6</td>\n",
" <td>4</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>7</td>\n",
" <td>4</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a4</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>8</td>\n",
" <td>2</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>8</td>\n",
" <td>9</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"text/plain": [
"clvl3 z1 z2\n",
"rlvl1 rlvl2 rlvl3 \n",
"a1 b1 c2 3 4\n",
" b2 c2 7 5\n",
"a2 b1 c2 6 4\n",
" b2 c2 7 4\n",
"a4 b1 c2 8 2\n",
" b2 c2 8 9"
]
},
"metadata": {},
"output_type": "display_data"
},
{
"data": {
"text/html": [
"<div>\n",
"<table border=\"1\" class=\"dataframe\">\n",
" <thead>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl1</th>\n",
" <th colspan=\"2\" halign=\"left\">x1</th>\n",
" <th colspan=\"2\" halign=\"left\">x2</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl3</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>rlvl1</th>\n",
" <th>rlvl2</th>\n",
" <th>rlvl3</th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" </tr>\n",
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" <tbody>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a1</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>3</td>\n",
" <td>4</td>\n",
" <td>5</td>\n",
" <td>6</td>\n",
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" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
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" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a2</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>6</td>\n",
" <td>4</td>\n",
" <td>9</td>\n",
" <td>3</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>7</td>\n",
" <td>4</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a4</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>8</td>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c2</th>\n",
" <td>8</td>\n",
" <td>9</td>\n",
" <td>6</td>\n",
" <td>1</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"text/plain": [
"clvl1 x1 x2 \n",
"clvl2 y1 y1 \n",
"clvl3 z1 z2 z1 z2\n",
"rlvl1 rlvl2 rlvl3 \n",
"a1 b1 c2 3 4 5 6\n",
" b2 c2 7 5 4 7\n",
"a2 b1 c2 6 4 9 3\n",
" b2 c2 7 4 3 7\n",
"a4 b1 c2 8 2 4 7\n",
" b2 c2 8 9 6 1"
]
},
"metadata": {},
"output_type": "display_data"
}
],
"source": [
"display(df.loc[(('a1','a2','a4'), ('b1','b2'), ('c2')), :])\n",
"display(df.loc[(('a1','a2','a4'), ('b1','b2'), ('c2')), 'x1'])\n",
"display(df.loc[(('a1','a2','a4'), ('b1','b2'), ('c2')), ('x1','y1')])\n",
"display(df.loc[(('a1','a2','a4'), ('b1','b2'), ('c2')), (('x1','x2'),('y1'))])"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"To select all indices at a particular level, a `slice(None)` can be used in place of a tuple. (`slice(None)` takes the place of `:` here since a colon inside a tuple is illegal python syntax).\n",
"\n",
"Just as in the last section, using a `slice(None)` at any index level will assure that the MultiIndex from the original DataFrame is kept intact."
]
},
{
"cell_type": "code",
"execution_count": 6,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
"<div>\n",
"<table border=\"1\" class=\"dataframe\">\n",
" <thead>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl1</th>\n",
" <th colspan=\"4\" halign=\"left\">x1</th>\n",
" <th colspan=\"4\" halign=\"left\">x2</th>\n",
" <th colspan=\"4\" halign=\"left\">x3</th>\n",
" <th colspan=\"4\" halign=\"left\">x4</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl3</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>rlvl1</th>\n",
" <th>rlvl2</th>\n",
" <th>rlvl3</th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a1</th>\n",
" <th>b1</th>\n",
" <th>c1</th>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>2</td>\n",
" <td>3</td>\n",
" <td>5</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c1</th>\n",
" <td>4</td>\n",
" <td>0</td>\n",
" <td>5</td>\n",
" <td>7</td>\n",
" <td>0</td>\n",
" <td>4</td>\n",
" <td>8</td>\n",
" <td>5</td>\n",
" <td>7</td>\n",
" <td>1</td>\n",
" <td>9</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a2</th>\n",
" <th>b1</th>\n",
" <th>c1</th>\n",
" <td>3</td>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>2</td>\n",
" <td>8</td>\n",
" <td>5</td>\n",
" <td>7</td>\n",
" <td>0</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>2</td>\n",
" <td>5</td>\n",
" <td>1</td>\n",
" <td>4</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c1</th>\n",
" <td>8</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>7</td>\n",
" <td>9</td>\n",
" <td>8</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>6</td>\n",
" <td>1</td>\n",
" <td>8</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" <td>9</td>\n",
" </tr>\n",
" <tr>\n",
" <th rowspan=\"2\" valign=\"top\">a4</th>\n",
" <th>b1</th>\n",
" <th>c1</th>\n",
" <td>7</td>\n",
" <td>1</td>\n",
" <td>6</td>\n",
" <td>1</td>\n",
" <td>7</td>\n",
" <td>2</td>\n",
" <td>6</td>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
" <td>3</td>\n",
" <td>2</td>\n",
" <td>9</td>\n",
" <td>4</td>\n",
" <td>0</td>\n",
" <td>2</td>\n",
" </tr>\n",
" <tr>\n",
" <th>b2</th>\n",
" <th>c1</th>\n",
" <td>9</td>\n",
" <td>3</td>\n",
" <td>8</td>\n",
" <td>6</td>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>8</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>4</td>\n",
" <td>1</td>\n",
" <td>5</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>3</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"text/plain": [
"clvl1 x1 x2 x3 x4 \n",
"clvl2 y1 y2 y1 y2 y1 y2 y1 y2 \n",
"clvl3 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2\n",
"rlvl1 rlvl2 rlvl3 \n",
"a1 b1 c1 2 4 3 7 5 3 6 9 0 5 8 3 6 2 3 5\n",
" b2 c1 4 0 5 7 0 4 8 5 7 1 9 4 7 6 6 6\n",
"a2 b1 c1 3 2 4 2 8 5 7 0 4 6 3 7 2 5 1 4\n",
" b2 c1 8 9 0 7 9 8 0 3 7 6 1 8 9 0 3 9\n",
"a4 b1 c1 7 1 6 1 7 2 6 2 4 7 3 2 9 4 0 2\n",
" b2 c1 9 3 8 6 2 4 8 5 8 4 1 5 4 6 3 3"
]
},
"metadata": {},
"output_type": "display_data"
}
],
"source": [
"display(df.loc[(('a1','a2','a4'), slice(None), ('c1')), :]) # select all indices at row level 2"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Some ambiguous cases <a id=\"ambiguities\"></a>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Remember how I said in the section [above](#arbitrary_multi-indexing) that for arbitrary multi-indexing you *had* to specify a column index for it to work? I lied :) This actually isn't always necessary. For example the following two are equivalent"
]
},
{
"cell_type": "code",
"execution_count": 7,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/plain": [
"True"
]
},
"execution_count": 7,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"result1 = df.loc[('a1','a2','a4'), ('b1','b2'), ('c2')] # incomplete indexing\n",
"result2 = df.loc[(('a1','a2','a4'), ('b1','b2'), ('c2')),:] # explicit column indexing\n",
"np.all(result1 == result2)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"The problem with this type of **incomplete indexing** with multi-index dataframes is that the behavior isn't always well defined. Specifically, when the number of index tuples is 1 or 2, pandas has no way of knowing which index tuples belong to the row index and which belong to the column index.\n",
"\n",
"This is actually a python limitation. You see, indexing with 2 tuples *without* specifying a column index is of the form\n",
"\n",
"`df.loc[( (level1 indices), (level2 indices) )]`\n",
"\n",
"But in the context of the `__getitem__` interface, this notation is exactly equivalent to \n",
"\n",
"`df.loc[(level1 indices), (level2 indices)]`\n",
"\n",
"In pandas, this case will always be interpreted as the typical row and column indexing.\n",
"\n",
"Funnily enough, simply appending a comma after the parenthesis will eliminate this ambiguity\n",
"\n",
"`df.loc[( (level1 indices), (level2 indices) ),]` <-- Note the added comma!"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"In summary, incomplete indexing with 3 or more indexing tuples works"
]
},
{
"cell_type": "code",
"execution_count": 8,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
"<div>\n",
"<table border=\"1\" class=\"dataframe\">\n",
" <thead>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl1</th>\n",
" <th colspan=\"4\" halign=\"left\">x1</th>\n",
" <th colspan=\"4\" halign=\"left\">x2</th>\n",
" <th colspan=\"4\" halign=\"left\">x3</th>\n",
" <th colspan=\"4\" halign=\"left\">x4</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" </tr>\n",
" <tr>\n",
" <th></th>\n",
" <th></th>\n",
" <th>clvl3</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>rlvl1</th>\n",
" <th>rlvl2</th>\n",
" <th>rlvl3</th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <th>a1</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>3</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" <td>5</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>2</td>\n",
" <td>9</td>\n",
" <td>8</td>\n",
" <td>1</td>\n",
" <td>8</td>\n",
" <td>7</td>\n",
" <td>0</td>\n",
" <td>6</td>\n",
" <td>0</td>\n",
" </tr>\n",
" <tr>\n",
" <th>a2</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>6</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>9</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>0</td>\n",
" <td>3</td>\n",
" <td>1</td>\n",
" <td>2</td>\n",
" <td>3</td>\n",
" <td>5</td>\n",
" <td>9</td>\n",
" <td>8</td>\n",
" <td>3</td>\n",
" </tr>\n",
" <tr>\n",
" <th>a4</th>\n",
" <th>b1</th>\n",
" <th>c2</th>\n",
" <td>8</td>\n",
" <td>2</td>\n",
" <td>7</td>\n",
" <td>9</td>\n",
" <td>4</td>\n",
" <td>7</td>\n",
" <td>8</td>\n",
" <td>2</td>\n",
" <td>2</td>\n",
" <td>0</td>\n",
" <td>9</td>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>6</td>\n",
" <td>4</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"text/plain": [
"clvl1 x1 x2 x3 x4 \n",
"clvl2 y1 y2 y1 y2 y1 y2 y1 y2 \n",
"clvl3 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2\n",
"rlvl1 rlvl2 rlvl3 \n",
"a1 b1 c2 3 4 6 6 5 6 3 2 9 8 1 8 7 0 6 0\n",
"a2 b1 c2 6 4 6 3 9 3 6 0 3 1 2 3 5 9 8 3\n",
"a4 b1 c2 8 2 7 9 4 7 8 2 2 0 9 7 5 8 6 4"
]
},
"execution_count": 8,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"df.loc[('a1','a2','a4'), ('b1','b3'), ('c2')]"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"But this does not work when using only 2 (or less) indexing tuples"
]
},
{
"cell_type": "code",
"execution_count": 13,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"KeyError: ('a1', 'a2', 'a4')\n"
]
}
],
"source": [
"try:\n",
" df.loc[('a1','a2','a4'), ('b1','b3')]\n",
"except KeyError as e:\n",
" print \"KeyError:\",e.message"
]
},
{
"cell_type": "code",
"execution_count": 10,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"KeyError: the label [a2] is not in the [columns]\n"
]
}
],
"source": [
"try:\n",
" df.loc[('a1','a2','a4')] # remember: this is the same as df.loc['a1','a2','a4'] to python\n",
"except KeyError as e:\n",
" print \"KeyError:\",e.message"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Perhaps surprisingly, in cases where you only need to specify a single index at every level of the row index this type of shorthand indexing will always work - even if the length of the index tuple is 2."
]
},
{
"cell_type": "code",
"execution_count": 11,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
"<div>\n",
"<table border=\"1\" class=\"dataframe\">\n",
" <thead>\n",
" <tr>\n",
" <th>clvl1</th>\n",
" <th colspan=\"4\" halign=\"left\">x1</th>\n",
" <th colspan=\"4\" halign=\"left\">x2</th>\n",
" <th colspan=\"4\" halign=\"left\">x3</th>\n",
" <th colspan=\"4\" halign=\"left\">x4</th>\n",
" </tr>\n",
" <tr>\n",
" <th>clvl2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" <th colspan=\"2\" halign=\"left\">y1</th>\n",
" <th colspan=\"2\" halign=\"left\">y2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>clvl3</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" <th>z1</th>\n",
" <th>z2</th>\n",
" </tr>\n",
" <tr>\n",
" <th>rlvl3</th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" <th></th>\n",
" </tr>\n",
" </thead>\n",
" <tbody>\n",
" <tr>\n",
" <th>c1</th>\n",
" <td>2</td>\n",
" <td>4</td>\n",
" <td>3</td>\n",
" <td>7</td>\n",
" <td>5</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>9</td>\n",
" <td>0</td>\n",
" <td>5</td>\n",
" <td>8</td>\n",
" <td>3</td>\n",
" <td>6</td>\n",
" <td>2</td>\n",
" <td>3</td>\n",
" <td>5</td>\n",
" </tr>\n",
" <tr>\n",
" <th>c2</th>\n",
" <td>3</td>\n",
" <td>4</td>\n",
" <td>6</td>\n",
" <td>6</td>\n",
" <td>5</td>\n",
" <td>6</td>\n",
" <td>3</td>\n",
" <td>2</td>\n",
" <td>9</td>\n",
" <td>8</td>\n",
" <td>1</td>\n",
" <td>8</td>\n",
" <td>7</td>\n",
" <td>0</td>\n",
" <td>6</td>\n",
" <td>0</td>\n",
" </tr>\n",
" </tbody>\n",
"</table>\n",
"</div>"
],
"text/plain": [
"clvl1 x1 x2 x3 x4 \n",
"clvl2 y1 y2 y1 y2 y1 y2 y1 y2 \n",
"clvl3 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2 z1 z2\n",
"rlvl3 \n",
"c1 2 4 3 7 5 3 6 9 0 5 8 3 6 2 3 5\n",
"c2 3 4 6 6 5 6 3 2 9 8 1 8 7 0 6 0"
]
},
"execution_count": 11,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"df.loc['a1','b1']"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"This works because pandas tries first to match the second index (`b1` in our example) to the column index and falls back to the row index if it is not found. Clearly this behavior has some consequences if your row and column Index's are not unique, so take care."
]
}
],
"metadata": {
"kernelspec": {
"display_name": "Python 2",
"language": "python",
"name": "python2"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 2
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython2",
"version": "2.7.6"
}
},
"nbformat": 4,
"nbformat_minor": 0
}
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