FITSIO HDU types demo

fitsio-hdu-types.ipynb

{
 "metadata": {
  "language": "Julia",
  "name": "",
  "signature": "sha256:cecac9bd2bf10399ce57d7b5689a4b9bc13dc79ad4193687854aedc6babd9661"
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "using FITSIO"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Writing an image to a file"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Open the file for write\n",
      "f = FITS(\"test.fits\", \"w\"); # \"r\" (read-only), \"r+\" (read-write), \"w\" (clobber)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 14,
       "text": [
        "file: test.fits\n",
        "mode: w\n",
        "extnum exttype         extname\n"
       ]
      }
     ],
     "prompt_number": 14
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# suppose we have some image data\n",
      "data = rand(5,3);"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 14
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Write the image to the fits file (creates a new image extension)\n",
      "write(f, data)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 15
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# extension has been added\n",
      "f"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 16,
       "text": [
        "file: test.fits\n",
        "mode: w\n",
        "extnum exttype         extname\n",
        "1      image_hdu       \n"
       ]
      }
     ],
     "prompt_number": 16
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "close(f)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 17
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Reading from a file"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Open the file in read-only mode\n",
      "f = FITS(\"test.fits\", \"r\")"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 18,
       "text": [
        "file: test.fits\n",
        "mode: r\n",
        "extnum exttype         extname\n",
        "1      image_hdu       \n"
       ]
      }
     ],
     "prompt_number": 18
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "length(f)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 19,
       "text": [
        "1"
       ]
      }
     ],
     "prompt_number": 19
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "f[1]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 20,
       "text": [
        "file: test.fits\n",
        "extension: 1\n",
        "type: IMAGE\n",
        "image info:\n",
        "  bitpix: -64\n",
        "  size: (5,3)"
       ]
      }
     ],
     "prompt_number": 20
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# read the data\n",
      "data = read(f[1])"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 21,
       "text": [
        "5x3 Array{Float64,2}:\n",
        " 0.325731  0.630665  0.113141\n",
        " 0.904424  0.277356  0.75392 \n",
        " 0.310158  0.871586  0.999169\n",
        " 0.862666  0.719114  0.750297\n",
        " 0.321728  0.868971  0.869869"
       ]
      }
     ],
     "prompt_number": 21
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Alternative read syntax\n",
      "f[1][:, :]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 22,
       "text": [
        "5x3 Array{Float64,2}:\n",
        " 0.325731  0.630665  0.113141\n",
        " 0.904424  0.277356  0.75392 \n",
        " 0.310158  0.871586  0.999169\n",
        " 0.862666  0.719114  0.750297\n",
        " 0.321728  0.868971  0.869869"
       ]
      }
     ],
     "prompt_number": 22
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Read an image subset\n",
      "f[1][2:3, 2:end]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 23,
       "text": [
        "2x2 Array{Float64,2}:\n",
        " 0.277356  0.75392 \n",
        " 0.871586  0.999169"
       ]
      }
     ],
     "prompt_number": 23
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# You can get an HDU object to simplify notation\n",
      "hdu = f[1]\n",
      "hdu[2:3, 2:end]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 24,
       "text": [
        "2x2 Array{Float64,2}:\n",
        " 0.277356  0.75392 \n",
        " 0.871586  0.999169"
       ]
      }
     ],
     "prompt_number": 24
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Access after closing is \"safe\" (no segfault)"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "close(f)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 25
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "f"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "ename": "ErrorException",
       "evalue": "attempt to access closed FITS file",
       "output_type": "pyerr",
       "traceback": [
        "attempt to access closed FITS file",
        " in fits_assert_open at /home/kyle/.julia/v0.3/FITSIO/src/FITSIO.jl:70"
       ]
      }
     ],
     "prompt_number": 26
    }
   ],
   "metadata": {}
  }
 ]
}