strange error message
in [Matlab]
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From: stpatryck on 14 Sep 2009 04:03 Hello Folks, I typed in these commands: >> t=0:0.01:2*pi;s=t; >> x=cos(t).*cos(s);y=cos(t).*sin(s);z=sin(t); >> surf(x,y,z) I got the following error message: ??? Error using ==> surf at 78 Z must be a matrix, not a scalar or vector. What am I doing wrong???
From: James Tursa on 14 Sep 2009 04:22 stpatryck <stpatryck(a)gmail.com> wrote in message <ec15a73f-76ad-4291-a568-b615d121e464(a)v36g2000yqv.googlegroups.com>... > Hello Folks, > > I typed in these commands: > >> t=0:0.01:2*pi;s=t; > >> x=cos(t).*cos(s);y=cos(t).*sin(s);z=sin(t); > >> surf(x,y,z) > > I got the following error message: > > ??? Error using ==> surf at 78 > Z must be a matrix, not a scalar or vector. > > > What am I doing wrong??? Amazingly enough, the error message means exactly what it says! Your x and y inputs to surf form a mesh, and z forms the height at each mesh point. i.e., each combination of an x element and a y element needs to have a z element. So if x is an n-vector and y is an m-vector, then Z needs to be a m-by-n matrix. James Tursa
From: SaintPatrick on 17 Sep 2009 23:11 On Sep 14, 4:22 am, "James Tursa" <aclassyguy_with_a_k_not_...(a)hotmail.com> wrote: > stpatryck <stpatr...(a)gmail.com> wrote in message <ec15a73f-76ad-4291-a568-b615d121e...(a)v36g2000yqv.googlegroups.com>... > > Hello Folks, > > > I typed in these commands: > > >> t=0:0.01:2*pi;s=t; > > >> x=cos(t).*cos(s);y=cos(t).*sin(s);z=sin(t); > > >> surf(x,y,z) > > > I got the following error message: > > > ??? Error using ==> surf at 78 > > Z must be a matrix, not a scalar or vector. > > > What am I doing wrong??? > > Amazingly enough, the error message means exactly what it says! Your x and y inputs to surf form a mesh, and z forms the height at each mesh point. i.e., each combination of an x element and a y element needs to have a z element. So if x is an n-vector and y is an m-vector, then Z needs to be a m-by-n matrix. > > James Tursa I don't understand -- z shows up in the workspace as a matrix with the same dimensions as x and y. Since t is a matrix, z = sin(t) should also be a matrix.
From: James Tursa on 18 Sep 2009 01:01 SaintPatrick <patrickmyu(a)gmail.com> wrote in message <45341af6-364d-45e0-bcc2-3536c8ae52fe(a)g6g2000vbr.googlegroups.com>... > > I don't understand -- z shows up in the workspace as a matrix with the > same dimensions as x and y. Since t is a matrix, z = sin(t) should > also be a matrix. >> t=0:0.01:2*pi;s=t; >> x=cos(t).*cos(s);y=cos(t).*sin(s);z=sin(t); >> whos Name Size Bytes Class s 1x629 5032 double array t 1x629 5032 double array x 1x629 5032 double array y 1x629 5032 double array z 1x629 5032 double array So why do you think t and z should be matrices? Clearly t is a vector, and z is a vector also because it is sin of a vector. James Tursa
From: stpatryck on 20 Sep 2009 17:49
On Sep 18, 1:01 am, "James Tursa" <aclassyguy_with_a_k_not_...(a)hotmail.com> wrote: > SaintPatrick <patrick...(a)gmail.com> wrote in message <45341af6-364d-45e0-bcc2-3536c8ae5...(a)g6g2000vbr.googlegroups.com>... > > > I don't understand -- z shows up in the workspace as a matrix with the > > same dimensions as x and y. Since t is a matrix, z = sin(t) should > > also be a matrix. > >> t=0:0.01:2*pi;s=t; > >> x=cos(t).*cos(s);y=cos(t).*sin(s);z=sin(t); > >> whos > > Name Size Bytes Class > s 1x629 5032 double array > t 1x629 5032 double array > x 1x629 5032 double array > y 1x629 5032 double array > z 1x629 5032 double array > > So why do you think t and z should be matrices? Clearly t is a vector, and z is a vector also because it is sin of a vector. > > James Tursa Sorry, my bad, I meant "vector" instead of matrix. I should have been more specific. A vector is a 1 x n or n x 1 matrix. (Feel free to correct me if I'm mistaken.) Nevertheless, all of the variables have the same dimensions, so why the error message? t=0:0.01:2*pi;s=t; x=cos(t).*cos(s);y=cos(t).*sin(s);z=sin(t); surf(x,y,z) ??? Error using ==> surf at 78 Z must be a matrix, not a scalar or vector. Patrick |