Question

% Any1 Can Plot This data Values by using Contour3 Plot Command of Matlab.
x_lower=-100;
x_upper=100;
y_lower=-100;
y_upper=100;
Number_of_x_Steps=400;
Number_of_y_Steps=400;
dx=(x_upper-x_lower)/Number_of_x_Steps;
dy=(y_upper-y_lower)/Number_of_y_Steps;

for j=1:Number_of_y_Steps
for i=1:Number_of_x_Steps
ds=dx*dy;
x=x_lower+1*dx+(i-1)*dx;
y=y_lower+1*dy+(j-1)*dy;
end
end

Answer 1

I am guessing you want to contour plot the x or y variable? The way that the for loops are set up this won't be possible. Since the x and y variable aren't indexed for each iteration of the loop, they will override themselves. Thus once the loop finishes, x and y are just constants.

To do a contour plot, your plotting variable needs to be a matrix.

For example, I re-wrote the inside of the loop to create the matrix "out". Notice that the indexes of "out" are defined for every iteration of i and j, out(i,j). The result is the matrix "out" is a 400x400 matrix. Then the "contour3(out,40)" creates a contour plot of "out" with 40 contours.

for j=1:Number_of_y_Steps
for i=1:Number_of_x_Steps
out(i,j) = sin(0.02*i)+cos(0.02*j);
end
end

contour3(out,40)


On a side note, consider pre-allocating variables that grow under loops; it will speed up the calculations. Also consider vectorizing for loops; Matlab is much faster at vectorized calculations than iterations.