python - Contour plot, TypeError: Length of y must be number of rows in z -

i have created function 2 arguments, func(x,y). plot 2d contour plot, first func(x,y) vs. x, , func(x,y) vs. y.

i set numpy array x-values 20 values 5e4 8e4, , y-values 20 values 1e10 1e12. function func(x,y) takes these 2 arrays arguments.

so, set plot follows:

import matplotlib import matplotlib.pyplot plt  import numpy np import matplotlib.cm cm import matplotlib.mlab mlab  matplotlib.rcparams['xtick.direction'] = 'out' matplotlib.rcparams['ytick.direction'] = 'out'  x = np.logspace( 5e4, 8e4, num=20)  y = np.logspace(1e10, 1e12, num=20) z = np.asarray([ func(x, y), x ]) plt.figure() cs = plt.contour(x, y, z) plt.clabel(cs, inline=1, fontsize=10) 

the shapes numpy arrays are:

print x.shape print y.shape print z.shape 

which outputs

(20,) (20,) (2, 20) 

my error

typeerror: length of y must number of rows in z. 

why be? dimensions correct.

from the docs contour: "x , y must both 2-d same shape z, or must both 1-d such len(x) number of columns in z , len(y) number of rows in z." (this version 1d x , y.)

your basic problem here z needs rectangular, 20x20 in case. is, think of contour plot putting levels on image.

as best can figure out, here's working version that's along lines of want:

import pylab pb     import numpy np import matplotlib.pyplot plt  def f(x, y):     return np.log(x**2 + y**2)  x = np.logspace( np.log10(5e4), np.log10(8e4), num=20)  y = np.logspace(np.log10(5e4), np.log10(9e4), num=20) x, y = np.meshgrid(x, y)  z = f(x, y) print x print y print min(z.flat), max(z.flat), min(x), max(x), min(y), max(y)  plt.figure() cs = plt.contour(x, y, z) plt.clabel(cs, inline=1, fontsize=10)  pb.show() 

i think key you're not using meshgrid (although there other means of getting too).