Plot a 4th dimension as color

Hello,

I'm new using matlab and I'm having some troubles, I hope someone can help me.

Until now I was working with two var functions, like F=x+y; x and y goes from 1 to 4 so I used [x,y]=meshgrid(1:0.1:4,1:0.1:4) and then run the function F to obtain the values of F 31x31 and make the plot using mesh(x,y,F).

Now I need to incorporate a new var to F, like F=x+y+z. I would like to see F as surface like in the two var case and set the z var as a color. It's possible? I have been searching the forum without luck. I have also tried doc surf and doc scatter3 but I keep getting errors =( when I try to do something with [x,y,z]=meshgrid(1:0.1:4,1:0.1:4,1:0.1:4) and F 31x31x31.

please if someone could indicate me how to make this happen, I would appreciate

Answer 1

[Image Analyst]

I don't think you want or need a 4th dimension. You only need 2 dimensions. Dimension 1 = row, dimension 2 = column, value = index into a lookup table. In other words, you make up an indexed image where the value of F at (y, x) is an index into a pseudocolor lookup table. Try this code:

% Define image size.
rows = 300;
% Make x and y
[x, y] = meshgrid(1:rows, 1:rows);
% Make the z values.  
% Let's use the famous "peaks" function.
zValues = 20*peaks(rows);
% Make "F" an indexed image.
F = zeros(rows, rows, 'double');
for x = 1 : rows
  for y = 1 : rows
    F(y, x) = x + y + zValues(y, x);
  end
end
imshow(F, []);
% Apply colormap called "jet".
colorbar
colormap(jet(256));

[Rodrigo]

Mmm is not what I needed and I can't even make it work with my own functions and variables. Anyway I really appreciate your answer and effort, I'm just too new to mathlab to make it work thanks.

Answer 2

[Shashank Prasanna]

When using surf to plot the meshgrid, specify the C to be the color or the 4th dimension.

[Rodrigo]

Thanks for your reply Shashank.

I'm sorry, but could you tell me exactly what to do?. I'm really new in mathlab and I can't pull it off with your explanation + the surf page.

I just get tons of errors at this point =(

??? CData must be an M-by-N matrix or M-by-N-by-3 array Error in ==> graph3d.surfaceplot.surfaceplot>localConstructor at 136 h = graph3d.surfaceplot(argin{:}); Error in ==> graph3d.surfaceplot.surfaceplot at 7 h = localConstructor(varargin{:}); Error in ==> surf at 101 hh = double(graph3d.surfaceplot(args{:},'parent',parax));