Error Messages, dimension and plot2cart (Matlab)

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John Smith
John Smith 2014-10-6
评论： Star Strider 2014-10-6
Hi the following script gives back the errors.But im not sure why
"Error using .* Matrix dimensions must agree.
Error in pol2cart (line 22) x = r.*cos(th);
Error in SurfPlotQ1 (line 18) [x,y]= pol2cart(th,r);"
function graph=plot(c,P,rd,E,t,nu,K,w,y,r,th) ;
c=15;
P=15;
rd=15;
E=18*10^6;
t=0.08;
nu=0.3;
th=meshgrid(0:0.1:2.*pi);
w=meshgrid(0:0.1:rd);
r=meshgrid(0:0.1:rd);
[x,y]= pol2cart(th,r);
K= (E*t^3)/(12*(1-nu^2));
w=((P.*rd.^4)./(64.*K)).*(1-(r./rd).^2).^2+c;
mesh(x,y,w);
colorbar
end

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回答（1 个）

Star Strider
Star Strider 2014-10-6
编辑：Star Strider 2014-10-6
Use the linspace function to generate the arguments to meshgrid to calculate ‘th’, ‘w’, and ‘r’. That way you can specify all of them to have the same lengths. That will avoid the error you’re getting.
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John Smith
John Smith 2014-10-6
Now the errors are - "Error using mesh (line 76) Z must be a matrix, not a scalar or vector
Error in SurfPlotQ1 (line 29) mesh(x,y,w);" and i know its meant to look like this http://i.imgur.com/iz74iV8.jpg?1
function graph=plot(c,P,rd,E,t,nu,K,w,y,r,th) ;
c=15;
P=15;
rd=15;
E=18*10^6;
t=0.08;
nu=0.3;
th=meshgrid(linspace(0,2*pi,1));
w=meshgrid(linspace(0,rd,1));
r=meshgrid(linspace(0,rd,1));
[x,y]= pol2cart(th,r);
K= (E*t^3)/(12*(1-nu^2));
w=((P.*rd.^4)./(64.*K)).*(1-(r./rd).^2).^2+c;
surf(x,y,w);
colorbar
end
Star Strider
Star Strider 2014-10-6
The third argument to linspace is the length of the vector you want it to create. You’ve asked it to create a scalar with a lenght of 1, and it did!
Change the linspace calls to:
th=meshgrid(linspace(0,2*pi,100));
w=meshgrid(linspace(0,rd,100));
r=meshgrid(linspace(0,rd,100));
and it works.

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