[Numpy-discussion] simple problem with arange / roundoff

[Keith Goodman]

On 7/31/07, Eric Emsellem <emsellem at obs.univ-lyon1.fr> wrote:
> Here is an example:
>
> start = -30.
> end = 30.
> npix = 31
> step = (end - start) / (npix - 1.)
> gridX = num.arange(start-step/2., end+step/2., step)
> array([-31., -29., -27., -25., -23., -21., -19., -17., -15., -13., -11.,
>         -9.,  -7.,  -5.,  -3.,  -1.,   1.,   3.,   5.,   7.,   9.,  11.,
>         13.,  15.,  17.,  19.,  21.,  23.,  25.,  27.,  29.])
>
> As you can see, it does not go up to 31., but only to 29, although step
> is = 2.0

>> import numpy.matlib as M
>> M.linspace(-30,30,31)

array([-30., -28., -26., -24., -22., -20., -18., -16., -14., -12., -10.,
        -8.,  -6.,  -4.,  -2.,   0.,   2.,   4.,   6.,   8.,  10.,  12.,
        14.,  16.,  18.,  20.,  22.,  24.,  26.,  28.,  30.])