Plotting 3D graph in polar coordinates

I'm trying to plot a 3D graph of a function in polar coordinates. The function takes a different form at different values of r. a, b and multiplier are constants I've defined earlier in the code (a=11, b=60, multiplier =-14)

 r=0:1:60;
 theta=0:pi/30:2*pi;

 for i=1:61
            r(i)=i-1;
            if (r(i)<a)
                sigmar(i)=-p_i;
            else
                sigmar(i)=((1-((b^2)/(r(i)^2)))*multiplier);   
            end
  end

I've been trying to plot the 3D curve using

 [x,y]=pol2cart(theta, r);
 surf(x,y,sigmar)

but when I run the code, it keeps saying 'Data dimensions must agree.'

[madhan ravi]

a,p_i,multiplier? provide the datas

[Rachel Attwood]

constants that i've defined earlier in the code. have edited the question body

Answer 1

[madhan ravi]

 clear all
  r=0:1:60;
   theta=0:pi/30:2*pi;
   for i=1:61
              r(i)=i-1;
              if (r(i)<3)
                  sigmar(i)=-6;
              else
                  sigmar(i)=((1-((7^2)/(r(i)^2)))*-14);   %multiplier is a predefined constant
              end
   end

    [x,y]=pol2cart(theta, r);
    [X,Y]=meshgrid(x,y);
    sigmar=repmat(sigmar,61,1);
   surf(X,Y,sigmar)

[madhan ravi]

note I provided some fake datas to constant alter it according to your needs and experiment with it

[Rachel Attwood]

I tried this and I still get the same error: 'data dimensions must agree'

[madhan ravi]

but I got the plot , try clear all at the beginning of the code and try again

[Rachel Attwood]

Ah great, thanks. I've got a plot now. It's not quite how I expected it to look, so I'll keep playing around with it.

[madhan ravi]

Anytime :)