Griding with python

Question

I am trying to plot a picture like this in python.

enter image description here

I have three parameters for ploting. x:

[ 0.03570416  0.05201517  0.05418171  0.01868341  0.07116423  0.07547471]

y:

 [-0.32079484 -0.53330218 -1.02866859 -0.94808545 -0.51682506 -0.26788337]

z:

[-0.32079484 -0.53330218 -1.02866859 -0.94808545 -0.51682506 -0.26788337]

so x is x-axis and y is y-axis. however z is the intensity of the pixel. I come up with this code:

z = np.array(reals)
x = np.array(ra)
y = np.array(dec)
nrows, ncols = 10, 10 
grid = z.reshape((nrows, ncols))
plt.imshow(grid, extent=(x.min(), x.max(), y.max(), y.min()), interpolation='nearest', cmap=cm.gist_rainbow)
plt.title('This is a phase function')
plt.xlabel('ra')
plt.ylabel('dec')
plt.show()

However I get this error:

grid = z.reshape((nrows, ncols))
ValueError: total size of new array must be unchanged

ra, dec and reals are normal arrays with the same size. I calculated them before and then I create the numpy arrays with them

Given your example data, x.size should, but does not, equal nrows * ncols. — Rutger Kassies
– Rutger Kassies, Commented Mar 27, 2013 at 10:57

tom10 · Accepted Answer · 2013-03-27 15:35:33Z

1

The data you show is not consistent with making an image, but you could make a scatter plot with it.

The two basic types of plots for z values at (x,y) coordinate pairs are:

scatter plots, where for each (x,y) pair, a z-value is specified.
image (imshow, pcolor, pcolormesh, contour), where an x-axis with m regularly spaced values, and a y-axis with n regularly spaced values are specified, and then an array of z-values with size (m,n) is given.

Your data looks more like the former type, so I'm suggesting a scatter plot.

Here's what a scatter plot looks like (btw, your y and z values are the same, which if probably a mistake):

import numpy as np
import matplotlib.pyplot as plt

x = np.array([ 0.03570416, 0.05201517, 0.05418171, 0.01868341, 0.07116423, 0.07547471])
y = np.array([-0.32079484, -0.53330218, -1.02866859, -0.94808545, -0.51682506, -0.26788337])
z = np.array([-0.32079484, -0.53330218, -1.02866859, -0.94808545, -0.51682506, -0.26788337])

plt.scatter(x, y, c=z, s =250)        

plt.show()

enter image description here

edited Mar 27, 2013 at 15:35

answered Mar 27, 2013 at 15:28

tom10

69.5k11 gold badges133 silver badges143 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Jelly Joe Sep 15 at 19:36

If extending this to >1000 points you'll want to use the faster plot(x, y, marker="o", ls="") rather than scatter(x, y)

Collectives™ on Stack Overflow

Griding with python

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related