My tools of the trade for python programming.
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 

63 lines
1.5 KiB

#
# Created: 20140207
# Wirawan Purwanto
#
"""
wpylib.array_tools
Various tools for arrays (mainly, numpy array objects).
"""
import numpy
def array_indices_cond_1d(arr, cond):
"""Get the ordered list of array indices whose corresponding elements satisfy
a given condition.
Useful for conditional assignment or evaluation.
The input `cond' argument can be an ufunc-like function that evaluates
a logical expression in bulk for each of the arr's element.
Or it can be an array of logical values that has the same length as arr.
Example use case:
r = numpy.linspace(1.97, 3.5, num=150)
i_select = cond_indices_1d(r, r <= 2.5)
# ... then we can do something with r[i_select]
# for conditional assignment or value extraction.
"""
arr = numpy.asarray(arr)
assert len(arr.shape) == 1
if callable(cond):
cond = cond(arr)
# otherwise, assume cond is already a good array
return numpy.array(xrange(len(arr)))[ cond ]
def array_hstack(arrays):
"""Creates a 2D array by horizontally stacking many arrays together
(along the array's second dimension).
Each of the input arrays can be a 1D or 2D array.
This function is similar to numpy.hstack.
"""
from numpy import asarray, hstack
stk = []
for a1 in arrays:
a = asarray(a1)
dim = len(a.shape)
if dim == 1:
a = a.reshape((len(a),1))
elif dim == 2:
pass
else:
raise ValueError, "Won't take 3D, 4D, ... arrays"
stk.append(a)
return hstack(stk)