I wanted to plot using imshow in a manner similar to the second example here http://www.scipy.org/Plotting_Tutorial but to redefine the scale for the axis. I'd also like the image to stay still while I do this!
The code from the example:
from scipy import * from pylab import * # Creating the 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 a line plot slicing the z matrix just for fun. plot(x[:], z[50, :]) show()
If I modify the extent to be wider, eg:
imshow(z, origin='lower', extent=[-4,4,-1,1])
Then the resulting image is stretched. But all I wanted to do was change the ticks to coincide with my data. I know I can use pcolor to conserve the X and Y data, though that has other ramifications to it.
I found this answer which allows me to manually redo all the ticks:
But that seems a bit overkill.
Is there a way to only change the extent shown by the labels?
help(imshow) will find the
aspect argument, which after a bit of experimentation seems to give what you want (a square image of the spiral but with x scale from -4 to 4 and y from -1 to 1) when used like this:
imshow(z, origin='lower', extent=[-4,4,-1,1], aspect=4)
But now your
plot is still from -1 to 1, so you'd have to modify that as well...
plot(x[:]*4, z[50, :])
I think when you have several elements that would have to be modified, just using a one-line tick relabeling instead isn't overkill:
xticks(xticks(), [str(t*4) for t in xticks()])