assignment of colormap to values in matrix

Hi, I'm plotting a surface with the help of mesh function.

I want to assign 'jet' color map to matrix A, and use it's absolute values in mesh. I want the minimum (of A) to be blue and the maximun to be red.

A, n1, n2, n3 all matrixes of the same size

B=abs(A)

x=(B.*n1);

y=(B.*n2);

z=(B.*n3);

mesh(x,y,z)

Not sure how to do it, thank you.

[Cris LaPierre]

Save your variables A,n1,n2,n3 to a mat file and attach to you post using the paperclip icon. At the least, tell us the dimensions of each of them.

[Tatiana Diachenko]

Hi, Thank you

They are matricess of 361*361.

n1 n2 n3 defines a sphere with the radius 1. and A is some function .

n1=sind(theta).*cosd(phi)'

n2=sind(theta).*sind(phi)'

n3= cosd(theta).*ones(1,361)'

theta=0:0.5:180

phi=0:360

Answer 1

[Walter Roberson]

Are you sure?

The fact that you take abs(A) implies that A is expected to have either negative or complex values. Maximum and minimum of complex values are not defined, so you must be expected A to have negative values.

If your n3 might have negative values, then your z will have negative values. But if n3 might be less than negative 1 then your z could have values more negative than the minimum of A; if your n3 might have values greater than 1 then your z values could have values more positive then the maximum of A. If your n3 is restricted to positive, then z would have to be strictly non-negative and you would be wasting a lot of the color space since you want the color mapping to start from the mininum of A, not from the minimum absolute value of A...

sz = [48, 64];
A = randn(sz);
n1 = rand(sz);
n2 = rand(sz);
n3 = rand(sz);

B = abs(A);
x = B .* n1;
y = B .* n2;
z = B .* n3;
mesh(x, y, z);
caxis([min(A(:)), max(A(:))]);
colormap(jet);
colorbar();

[Tatiana Diachenko]

Hi, Thank you,

n3 has negative values that are smaller than 1, and A is not complex.

n1,n2.n3 define a sphere of radius 1.

n1=sind(theta).*cosd(phi)'

n2=sind(theta).*sind(phi)'

n3= cosd(theta).*ones(1,361)'

theta=0:0.5:180

phi=0:360

if I don't use abs(A) I get only half of my surface, but when I plot the surface with abs(A), I want to distinguish what values were negative and what values were positive in A with the colormap.