# How to plot a function with 3 independent variables

62 views (last 30 days)
Seng Hkawn N-Sang on 13 Oct 2021
Commented: Seng Hkawn N-Sang on 15 Oct 2021
f(x,y,z)=0.95*x+0.73*y+0.62*z-130.05
f(x,y,z); x; y; and z are values between 0 and 100.
f(x,y,z) is shown in color. How can I plot in MATLAB similar to figure below.
Thank you!
Walter Roberson on 13 Oct 2021
slice()
Or possibly isosurface() called several times

KSSV on 13 Oct 2021
f = @(x,y,z) 0.95*x+0.73*y+0.62*z-130.05 ;
x = linspace(0,100) ;
y = linspace(0,100) ;
z = linspace(0,100) ;
[X,Y,Z] = meshgrid(x,y,z) ;
V = f(X,Y,Z) ;
isosurface(X,Y,Z,V,1e-4)
Walter Roberson on 14 Oct 2021
f = @(x,y,z) 0.95*x+0.73*y+0.62*z-130.05 ;
x = linspace(60,100) ;
y = linspace(60,100) ;
z = linspace(60,100) ;
[X,Y,Z] = meshgrid(x,y,z) ;
V = f(X,Y,Z) ;
Vmin = min(V(:))
Vmin = 7.9500
Vmax = max(V(:))
Vmax = 99.9500
levels = 70:5:100;
Nlevels = length(levels);
cmap = hot(Nlevels);
for K = 1 : Nlevels
s = isosurface(X, Y, Z, V, levels(K));
p(K) = patch(s);
p(K).EdgeColor = 'none';
p(K).FaceColor = cmap(K,:);
isonormals(X, Y, Z, V, p(K));
end
camlight;
lighting gouraud;
xlim auto; ylim auto; zlim auto
view(3); view(36, 64);
legend(p, string(levels))
You cannot do contour lines because you are dealing with a 3D object: you can only do ISO surfaces.
It might be possible to get the colors right without some of the above steps. With the default steps I showed in https://www.mathworks.com/matlabcentral/answers/1562461-how-to-plot-a-function-with-3-independent-variables#comment_1783116 you might notice that the colors come out wrong compared to the legend: it turns out that you are looking at the "back" of the plates, and that you need to view() to see the front (or you need to move the light.)
Seng Hkawn N-Sang on 15 Oct 2021
Thank you both!
Got it working!

### Categories

Find more on Lighting, Transparency, and Shading in Help Center and File Exchange

R2021b

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!