MATLAB: Plot a family of circles in 3D

for loopMATLABplot

I have the following code for plotting 100 circles in separate height planes where the radius increases from 1 to 100.
if true
  for r=1:1:100
  t=linspace(0,2*pi);
  x=r*cos(t);
  y=r*sin(t);
  for h=100:100:10000   
    z = 100 * r * ones(1, length(t));
    plot3(x,y,z);
    if r == 1 && h == 100
      hold on;
      set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
    end
    drawnow;
  end
end
Like this:
[1]: http://i.stack.imgur.com/dsPX1.png
*Question*
Now I want to change the code in order for the radius to *decrease* from 100 to 1, i.e turn the cone upside down. So the code should probably read like this but i can't get it to work:
    for r=100:-1:1
  t=linspace(0,2*pi);
  x=r*cos(t);
  y=r*sin(t);
  for h=100:100:10000   
    z = 100 * r * ones(1, length(t));
    plot3(x,y,z);
    if r == 100 && h == 100
      hold on;
      set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
    end
    drawnow;
  end
end

Best Answer

The height is controlled by 'z' and not 'h'. In the first case, when r=1, z= 100*1*k (where k=ones(1, length(t))). If you want to reverse the cone then, z should be 100*1*k when r=100. Which means:
z = 100 * (101-r) * ones(1, length(t));
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