Plot3 with different colors depending on the value of Z

I am trying to create something like a contour plot but only with vectors. To be more specific, I have 3 vectors of equal lengths and I am using plot3 to visualize their data. Now I am trying to add colors depending on the Z value. I have written the following code, but it doesn't work and I don't know why:

max_iter = find(n_iter(2:end)==0);
MAX = n_iter(max_iter);
MAXVAL = optValues(max_iter);
color = ['b','g','y','r'];
for i = 1:length(MAXVAL)
    if(MAXVAL(i) < 1)
        plot3(1:1:i,MAX(i),MAXVAL(i),color(1)); hold on;
    elseif (MAXVAL(i) < 50)
        plot3(1:1:i,MAX(i),MAXVAL(i),color(2));hold on;
    elseif (MAXVAL(i) < 400)
        plot3(1:1:i,MAX(i),MAXVAL(i),color(3));hold on;
    else
        plot3(1:1:i,MAX(i),MAXVAL(i),color(4));hold on;
    end
end
grid on;
xlabel('Simulation time steps');ylabel('Iteration');zlabel('Objective Function Value'); 

By "it doesn't work" I mean that MATLAB is busy without producing any results.

Answer 1

[KSSV]

Let (x,y,z) be your m*3 data. Two options:

If data is structured

x = unique(x) ; nx = length(x) ; 
y = unique(y) ; ny = length(y) ; 
[X,Y] = meshgrid(x,y) ;
Z = reshape(z,nx,ny) ; 
contour(X,Y,Z) ;

If data is unstructured:

m = 100 ; n = 100 ; 
xi = linspace(min(x),max(x),m) ; 
yi = linspace(min(y),max(y),n) ; 
[X,Y] = meshgrid(xi,yi) ; 
Z = griddata(x,y,z,X,Y) ;
contour(X,Y,Z)

[patr chri]

Thank you very much for your answer but your suggestion doesn't implement what I had in mind.

I want to have like a plot3 form (one 3d line connecting between points defined by vectors x and y, but depending on the height (z vector) of this line to have different colors).

For example, in the following figure the marked region with yellow will be red and accordingly the rest of the plot will have other colors.

[KSSV]

Have a look on scatter function.

[KSSV]

Or try does this fit in your case.

https://in.mathworks.com/matlabcentral/answers/5042-how-do-i-vary-color-along-a-2d-line

[Image Analyst]

What would you do if you have 3 points and each one is in a different color zone? What color would the line between each pair of points take on???

[patr chri]

Your last suggestion worked.

Thank you!

[patr chri]

@Image Analyst

I would need to interpolate in between them in order to generate seperate color areas, I think. What would be your suggestion?