constrain surf() plot region
3 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
Hi all, I'm working with the surf(X,Y,Z) function, and trying to force some values to be specific. I'm basically trying to plot a 3D sin-wave, rotationally symmetric about (0,0) and contain a specific number of waves in any direction, then outside this region, force the Z values to zero. Here's code attempts using an 'if' but the Z=0 isn't applied at larger radii than Xmax:
NumberWaves = 2;
Each_Division = 0.1;
X_max = NumberWaves * (2 * pi) ;
X_min = -X_max;
Y_min = X_min;
Y_max = X_max;
[X,Y] = meshgrid(X_min : Each_Division : X_max);
Rad = sqrt (X.^2 + Y.^2 );
if (Rad < X_max)
Z=0;
else
Z = (((sin(Rad)) + 1) / 2);
end
figure;
colormap hsv;
surf(X,Y,Z, 'EdgeColor' ,'None');
xlabel('X (**)');ylabel('Y (**)');zlabel('Red Scale');
Alternatively to the forcing Z to a value, I was trying to find references to only plot the surface out to a given radius, which again would be rotationally symmetric. I'm very new to Matlab, so any help appreciated! Thanks!
0 commentaires
Réponse acceptée
Kelly Kearney
le 10 Nov 2014
I would recommend setting up your grid in polar coordinates. The surf command (along with mesh, pcolor, etc.) doesn't require a rectilinear grid, so starting in terms of r and theta allows you to set the cutoff exactly without any setting-to-0 or NaN-masking:
NumberWaves = 2;
Each_Division = 0.1;
rmax = NumberWaves * (2 * pi) ;
r = linspace(0, rmax, 50);
theta = linspace(0, 2*pi, 100);
[r,theta] = meshgrid(r, theta);
z = (sin(r) + 1)./2;
x = r .* cos(theta);
y = r .* sin(theta);
surf(x,y,z);
5 commentaires
Kelly Kearney
le 11 Nov 2014
Just so you know, you've got some unnecessary calculations there. You can get the same with
cmap = [linspace(0,1,101)' zeros(101,2)];
Plus de réponses (1)
Voir également
Catégories
En savoir plus sur Lighting, Transparency, and Shading dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!