Error Messages, dimension and plot2cart (Matlab)

2014 10 6
1 个回答
更新时间：2014 10 6
1 次查看（30 天）

0 个投票

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

请先登录，再回答此问题。

回答（1 个）

Star Strider
Star Strider 2014-10-6
编辑：Star Strider 2014-10-6

0 个投票

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.

4 个评论
显示 2更早的评论 隐藏 2更早的评论

John Smith
John Smith 2014-10-6
Thanks for the reply! but would i have to replace meshgrid with linspace, or just do it after meshgrid?
Star Strider
Star Strider 2014-10-6
My pleasure!
You can do linspace outside meshgrid or inside it. It’s all the same to the computer — neither is more efficient. This should work:
th=meshgrid(linspace(0,2*pi,250));
The choice of 250 is arbitrary. Just be sure it’s the same value for all three variables and you won’t get the ‘matrix dimensions must agree’ error. (You don’t want them arguing in any event!)
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.

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Logical 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by