MATLAB: Construct meshgrid matrices without using function meshgrid.

meshgrid matrices

Hi, I am going to construct meshgrid matrices1 x(i, j), y(i, j), given the grid points x=[0: 0.1:10], y=[0:0.2:10]. when I try x.*y.'. It can't go through. I know I can produce an mn matrix C with elements C(i, j) = x(i)y(j), i=1:m, j= 1:n. But I dunno how can I start with.

Best Answer

Try this:

% Sample data.
x = [0 : 1 : 10]  % Change the middle "step" number if you want.
y = [0 : 2 : 10]
% Traditional way using meshgrid().
[X, Y] = meshgrid(x, y)
% Alternate way using loop.
rows = length(y);
columns = length(x);
xLoop = zeros(rows, columns);
yLoop = zeros(rows, columns);
for column = 1 : length(x)
  xLoop(:, column) = x(column);
  yLoop(:, column) = y;
end
% Print to command window.
xLoop
yLoop

Related Solutions

MATLAB: 3d Plotting Using Meshgrid

Replace

for i=1:1:length(n)
    for j=1:1:length(m)
        [X,Y]=meshgrid(i,j);
        %disp(f(X,Y));       
        mesh(X,Y,f(X,Y));
    end
end

with

[X,Y] = meshgrid(1:length(n),1:length(m));
figure
surf(X,Y,f')

MATLAB: Meshgrid

I assume that x and y have the same values as x1 and y1, but in a different order. You could do a search for each pair (x1,y1), but it's faster to sort the coordinates and then reshape Z. Here is an example with an actual image to give you the idea:

%%Set up the problem
load mandrill
Z = X; %rename image
nrows = size(Z,1); ncols = size(Z,2);
[x1,y1] = meshgrid(1:nrows,1:ncols);
x = x1(:); y = y1(:); Z = Z(:);
% Scramble the elements.
index = randperm(numel(Z));
x = x(index); y = y(index); Z = Z(index);
%%Now the problem is set up, unscramble x and y and then reshape Z.
xy = [x y];
[~,index] = sortrows(xy,[1 2]);
x = x(index); y = y(index); Z = Z(index);
Z = reshape(Z,nrows,ncols);
image(Z)

Of course, if x and y were originally obtained from a process like that in the previous cell, you won't need to sort.

Best Answer

Related Solutions

MATLAB: 3d Plotting Using Meshgrid

MATLAB: Meshgrid

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