Rounding the elements of a Python array (numarray module)
From: Chris P. (chris.peressotti_at_utoronto.ca)
Date: 11/30/04
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Date: 30 Nov 2004 08:57:59 -0800
Hi. I have a very simple task to perform and I'm having a hard time
doing it.
Given an array called 'x' (created using the numarray library), is
there a single command that rounds each of its elements to the nearest
integer? I've already tried something like
>>> x_rounded = x.astype(numarray.Int)
but that only truncates each element (i.e. '5.9' becomes '5').
I've read over all the relevant numarray documentation, and it
mentions a bunch of Ufuncs that are available - there's 'floor' and
'ceil', but no 'round'. And when I try using the built-in function
'round' on an array like so
>>> x_rounded = round(x)
I get "TypeError: Only rank-0 numarray can be cast to floats."
So I created a bad function that uses nested loops, but my arrays are
600x600x3 elements (I'm doing some image processing after converting a
PIL Image to a numarray array) and it takes a REALLY long time. Has
anyone else had to do this, or knows of any tricks? Any help is
appreciated.
- Chris
P.S. Here's my "bad function"
# This code assumes that 'the_array' is a 3-dimensional array.
def ArrayRound(the_array):
result = numarray.zeros(the_array.shape)
if len(the_array.shape) == 3:
(depths,rows,columns) = the_array.shape
for depth in range(depths):
for row in range(rows):
for column in range(columns):
result[depth][row][column] = #continued
round(the_array[depth][row][column])
return result
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