doug ybarbo alexland

scala, spark, akka dev designing & building distributed systems--data pipelines, machine learning systems, search

alexland / package-name-expander.R

Created October 8, 2012 06:02

for programatic update of an R package--avoid having to use complete filename with version appended


	pkg_name = paste("~/path/to/package", system('cd /path/to/package; ls adStats*', intern=T), sep="/")

	install.packages(pkg_name, repos=NULL, type="source")

alexland / sort_tapply.R

Created October 10, 2012 02:13

sorting a data frame on a numeric variable conditioned on a factor variable


	DF1 = DF[order(DF$factor_var, -xtfrm(DF$numeric_var)),]
	DF1$idx = sequence(rle(as.character(DF1$factor_var))$lengths)


	$> # e.g., sort a data frame based on 'price' (numeric variable)
	$> # 'grouped by' the levels of 'color' (factor, or discrete variable)

	$> data(diamonds, package="ggplot2")

alexland / commify.R

Created July 3, 2013 22:45

add commas to numbers comprising various R objects (eg, tables)

print_fn = function(x) {print(format(x, big.mark=','), quote=F)}

alexland / exception_class_id.py

Created September 26, 2013 03:38

how to find the module an exception class was defined in


	try:
	...
	except Exception, e:
	print("caught an exception defined in class {0}".format(e.__class__.__module__))

alexland / flatten.py

Last active December 24, 2015 17:29

flatten a nested sequence: distinguishes lists from strings, etc.

	# first, a compact one-liner but limited to 2D sequences (nested just one level):

	# obvious, but
	# "nested_list" refers to the nested list you want to flatten,
	# "row" refers to each list comprising the nested_list
	# "itm" refers to each element comprising each row


	def flatten(list2D):
	return [itm for row in list2d for itm in row]

alexland / python idioms

Last active August 29, 2015 13:57

useful (but not common known) python idioms

	# useful eg, for recursive functions such as merge sort or binary tree building/traversal in which sometimes the fn must return one of two portions of some container (a sequence, tree node, etc.)

	def fnx(a):
	if a % 2 == 0:
	x = 45
	y = None
	else:
	x = None
	y = 3
	return (x or y) + 2

alexland / column-print.py

Last active March 26, 2019 13:21

printing formatted tables using python 3 "advanced string formatting"

	# let's say you have four sequences you want to print columnwise, like so:

	19 59 97 44
	92 57 63 68
	66 21 69 90
	75 66 12 19

	# mock some data
	import random as RND
	gen_row = lambda: [ RND.randint(10, 99) for c in range(3) ]

alexland / factorial.py

Created May 23, 2014 03:00 — forked from ghoseb/factorial.py

	#Newbie programmer
	def factorial(x):
	if x == 0:
	return 1
	else:
	return x * factorial(x - 1)
	print factorial(6)


	#First year programmer, studied Pascal

alexland / NLP-category-predict-ML-1.ipynb

Created May 30, 2014 21:41

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alexland / softmax-mlp.py

Last active August 29, 2015 14:02

for a multi-layer perceptron using softmax for output layer, transform output-layer vector to probability vector, then calculate cross-entropy error

	'''
	these 2 functions assume this sort of MLP architecture:
	(i) a classification problem modeled w/ softmax activation function
	(ii) encode the output layer w/ 1-of-N
	> so for raw data like this:
	.3, .2, .6, .1, 'class I'
	.6, .1, .8, .4, 'class II'
	.5, .2, .7, .3, 'class III'

	recode it for intput to a softmax MLP like so: