python - How do I change the scale of imshow in matplotlib without stretching the image? -

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i wanted plot using imshow in manner similar second example here http://www.scipy.org/plotting_tutorial redefine scale axis. i'd image stay still while this!

the code example:

from scipy import * pylab import *  # creating grid of coordinates x,y  x,y = ogrid[-1.:1.:.01, -1.:1.:.01]  z = 3*y*(3*x**2-y**2)/4 + .5*cos(6*pi * sqrt(x**2 +y**2) + arctan2(x,y))  hold(true) # creating image imshow(z, origin='lower', extent=[-1,1,-1,1])  xlabel('x') ylabel('y') title('a spiral !')  # adding line plot slicing z matrix fun.  plot(x[:], z[50, :])  show()

if modify extent wider, eg:

imshow(z, origin='lower', extent=[-4,4,-1,1])

then resulting image stretched. wanted change ticks coincide data. know can use pcolor conserve x , y data, though has other ramifications it.

i found answer allows me manually redo ticks:

how convert (or scale) axis values , redefine tick frequency in matplotlib?

but seems bit overkill.

is there way change extent shown labels?

a help(imshow) find aspect argument, after bit of experimentation seems give want (a square image of spiral x scale -4 4 , y -1 1) when used this:

imshow(z, origin='lower', extent=[-4,4,-1,1], aspect=4)

but plot still -1 1, you'd have modify well... 

plot(x[:]*4, z[50, :])

i think when have several elements have modified, using one-line tick relabeling instead isn't overkill:

xticks(xticks()[0], [str(t*4) t in xticks()[0]])

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