How do I create a 3 dimensional surface from X Y Z points

Hi all,

I am struggling a bit here, and hope somebody could help. I have a set of points from a complex function that I am trying to produce a 3D shape of, and have had no luck so far. I used Python to find the points in a .txt format. From there, I copy the data to Excel to transpose the columns into rows for Matlab use. The problem is, I can't seem to figure out a code to just take the X, Y, and Z coordinates and produce some kind of mesh grid or figure. Does anybody have a code for this?

Here is an example of just (10) points from my function. I can tell Python to produce anywhere from 10 to 10,000 points.

x = [422 424 424 422 422 421 421 425 421 424]; y = [87 96 87 87 83 93 85 88 86 91]; z = [92.73 94.88 92.92 92.73 92.04 93.92 92.24 93.23 92.42 93.78];

Best regards,

Eric.

Answer 1

[Star Strider]

Using the griddata (link) function is an option:

x = [422   424   424   422   422  421   421   425   421    424];
y = [87   96   87   87   83    93    85   88    86   91];
z = [92.73  94.88  92.92  92.73  92.04  93.92  92.24  93.23  92.42  93.78];

figure(1)
stem3(x, y, z)
grid on

xv = linspace(min(x), max(x), 20);
yv = linspace(min(y), max(y), 20);
[X,Y] = meshgrid(xv, yv);
Z = griddata(x,y,z,X,Y);

figure(2)
surf(X, Y, Z);
grid on
set(gca, 'ZLim',[0 100])
shading interp

Experiment to get the result you want.

[Stephen23]

Eric Verheyen's "Answer" moved here:

Thanks for the help, is there any way I can use the surf function or produce some kind of grid that shows the contours of my points?

[Star Strider]

My pleasure.

The griddata function will interpolate a varying surface if the variation exists. It produced a plane here because the plane defined the points provided. (See the documentation on griddata for details.)

I am not certain what you want. The surf function depicts a surface. The surfc function will provide an additional contour below the surface. The contour3 function will (with the hold function) draw contours on the surface. The contour and contourf functions will draw a contour plot.

@Stephen — Thank you.

[Sophia Dauenhauer]

Thank you so much... this helped me figure out plotting a 3d surface from given x y z data points.

[Star Strider]

@Sophia Dauenhauer — My pleasure!

[Felipe Alvarez Arroyo]

thankyou

[Star Strider]

@Felipe Alvarez Arroyo — My pleasure!

Votes are always appreciated!

Answer 2

[Shivam Anand]

x=[32 20 67 1 98 34 57 65 24 82 47 55 8 51 13 14 18 30 37 39 10 33 21 26 38 81 83 60 95 22 17 5 72 46 99 52 12 25 96 29 70 85 43 69 19 78 97 31 89 53 2 91 48 71 61 15 36 84 94 50 11 80 6 7 49 74 9 88 40 79 27 68 73 64 63 59 86 23 35 58 45 28 100 42 93 87 16 90 41 66 54 92 77 4 62 76 75 56 3 44];
y=[96 75 24 9 83 49 27 77 3 23 17 31 40 13 7 52 51 21 98 47 64 79 78 91 44 16 15 100 84 99 63 68 70 30 54 76 97 73 33 5 88 8 71 66 62 25 60 42 72 45 18 11 28 59 89 65 10 55 69 81 12 26 20 95 87 41 74 50 93 22 43 90 14 34 82 35 56 38 80 32 1 57 6 36 37 61 29 58 2 48 4 46 67 53 92 86 94 19 39 85];
z=[55 31 11 45 83 36 86 49 15 57 42 46 8 94 88 47 54 81 98 41 32 35 56 85 9 89 37 60 23 62 67 100 78 76 73 80 10 20 68 34 77 93 1 63 53 12 22 99 91 40 84 24 33 3 43 19 92 97 6 82 64 25 26 79 95 4 44 58 5 21 70 29 65 87 96 90 51 14 18 2 72 28 71 39 52 7 27 59 50 61 48 30 66 69 17 13 74 16 75 38];
xlin = linspace(min(x), max(x), 100);
ylin = linspace(min(y), max(y), 100);
[X,Y] = meshgrid(xlin, ylin);
% Z = griddata(x,y,z,X,Y,'natural');
% Z = griddata(x,y,z,X,Y,'cubic');
Z = griddata(x,y,z,X,Y,'v4');
mesh(X,Y,Z)
axis tight; hold on
plot3(x,y,z,'.','MarkerSize',15)

Answer 3

[Al Danial]

Since you're starting in Python you can make the surface plot there too if you want. This is a translation of @Star Strider's matlab solution:

#!/usr/bin/env python
import matplotlib.pyplot as plt
from matplotlib import cm
import numpy as np
from scipy.interpolate import griddata

x = np.array([422, 424, 424, 422, 422, 421, 421, 425,
              421, 424])
y = np.array([87, 96, 87, 87, 83, 93, 85, 88, 86, 91])
z = np.array([92.73, 94.88, 92.92, 92.73, 92.04, 93.92,
              92.24, 93.23, 92.42, 93.78])

xv = np.linspace(np.min(x), np.max(x), 20)
yv = np.linspace(np.min(y), np.max(y), 20)
[X,Y] = np.meshgrid(xv, yv)
Z = griddata((x,y),z,(X,Y),method='linear')
fig, ax = plt.subplots(subplot_kw={"projection": "3d"})
surf = ax.plot_surface(X, Y, Z, cmap=cm.coolwarm,
                       linewidth=0, antialiased=False)
ax.set_xlabel('X')
ax.set_ylabel('Y')
fig.colorbar(surf, shrink=0.6)
plt.show()