Contour a log fuction with n contour levels

I would like to create a contour of a log function with a multiple contour levels, but when N is included the figure turns out blank, the following is an example:

[i,j] = meshgrid(-50:1:50,-50:1:50);

for x=1:size(i,1)

      for y=1:size(j,1)

          R(x,y) = log(i(x,y)*j(x,y)); 

      end
  end
  contour(R,10);

Answer 1

[Honglei Chen]

There are negative numbers in log so the result may be complex. In addition, there is zero in log, so log(0) gives infinity, which cannot be dealt by contour. Are you sure you want log on such ranges?

BTW, you could have written

R = log(i.*j);

to save the two loops.

[Richard Brown]

or even better R = log(i .* j)

(no loops)

[Jhon]

actually no, i can manage the range to be strictly higher than 0

[Guo]

I agree with Richard,Matrix computation is the dominant feature of matlab.Matlab canbe more efficient in this form.