Thread Subject:

Linspace at a diagonal

I have a large grid of points and want to take the linspace across the diagonal (45 degree angle). How does one do this?

"Eric " <ericbchang@hotmail.com> wrote in message <gqipve$rln$1@fred.mathworks.com>...
> I have a large grid of points and want to take the linspace across the diagonal (45 degree angle). How does one do this?

I do not understand your problem. Can you give a small example of the expected input and output?

Jos

Are you talking about this, for example:

N = 6;
A = magic(N)
A(N:N-1:N^2-1)

if you want the other diagonal, you could use diag or

A(1:N+1:N^2)

"Eric " <ericbchang@hotmail.com> wrote in message <gqipve$rln$1@fred.mathworks.com>...
> I have a large grid of points and want to take the linspace across the diagonal (45 degree angle). How does one do this?

  You have not described your problem well, Eric, and we have to resort to wild guesses. Perhaps you mean something like the following. Assume your grid is m by n points. For some a and b do this:

 t = linspace(a,b,m+n-1);
 M = hankel(t(1:m),t(m:m+n-1));

  For the other diagonal direction, you would use the 'toeplitz' function.

Roger Stafford

"Roger Stafford" <ellieandrogerxyzzy@mindspring.com.invalid> wrote in message <gqj2vl$sv5$1@fred.mathworks.com>...
> "Eric " <ericbchang@hotmail.com> wrote in message <gqipve$rln$1@fred.mathworks.com>...
> > I have a large grid of points and want to take the linspace across the diagonal (45 degree angle). How does one do this?
>
> You have not described your problem well, Eric, and we have to resort to wild guesses. Perhaps you mean something like the following. Assume your grid is m by n points. For some a and b do this:
>
> t = linspace(a,b,m+n-1);
> M = hankel(t(1:m),t(m:m+n-1));
>
> For the other diagonal direction, you would use the 'toeplitz' function.
>
> Roger Stafford
I am trying to generate a 3D array plot using the meshgrid function. I am trying to isolate this generated plot into three bands (x axis, y axis, 45 degree line). I was able to generate the x and y axes, but am having difficulties isolating a 45 degree line. This is a sample of the code for the x and y axes.
[XX1,YY1] = meshgrid(linspace(min(xx),0.048,150),linspace(-0.035,-0.036,150));
[XX2,YY2] = meshgrid(linspace(0.048,0.049,150),linspace(-0.035,max(yy),150));
for tt = 1:1:nn,
    waitbar(tt/nn,h)
    cc=cc+1;
    zz= time_resp(:,tt);
    Wf1(:,:,cc)= griddata(xx,yy,zz,XX1,YY1,'linear');
    Wf2(:,:,cc)= griddata(xx,yy,zz,XX2,YY2,'linear');
pcolor(XX1,YY1,Wf1(:,:,cc));
    pcolor(XX2,YY2,Wf2(:,:,cc));
caxis([0.0 0.0003]), axis off, %
    C=colormap(gray); C=C(64:-1:1,:); colormap(C);
    shading interp;
    axis equal;
    
    M(:,cc)=getframe;
end

The numbers 0.048,-0.035 are just an arbitrary point on the plot.