On Mon, 18 Aug 2008 10:52:45 -0700, Alejandro wrote: > Hi: > > I need to find the multiples of a decimal number in a floating point > list. For instance, if a have the list [0,0.01,0.02,...1], I want the > multiples of 0.2: [0, 0.2,0.4,0.6,0.8,1]. > > With integers this problem is easy, just test for (i%n == 0), where i is > the number I am testing, and n is the multiple. Given the finite > resolution of floating point numbers, this is more complicated for > float. > > I came with this solution: > > from numpy import arange > from math import modf, fabs > > float_range = arange(0, 1, 0.01) > for f in float_range: > m = modf(f / 0.2)[0] > if m<1e-13 or fabs(1-m)<1e-13: > print f > # Do something else > > This code works, however, I found it a little ugly. Is there a better > way to do the same? > > Alejandro.
Hi Alejandro, you can do the same thing more efficiently (both in terms of lines of code and execution speed) by doing the whole array at once: from numpy import arange, absolute from math import modf, fabs float_range = arange(0, 1, 0.01) multiples = absolute(float_range % 0.2)<1e-13 # now multiples is a boolean array print float_range[multiples] HTH, Dan -- http://mail.python.org/mailman/listinfo/python-list
