Previous: Miscellaneous Techniques, Up: Vectorization and Faster Code Execution

### 19.6 Examples

The following are examples of vectorization questions asked by actual users of Octave and their solutions.

- For a vector `A`, the following loop

                n = length (A);
                B = zeros (n, 2);
                for i = 1:length(A)
                  ## this will be two columns, the first is the difference and
                  ## the second the mean of the two elements used for the diff.
                  B(i,:) = [A(i+1)-A(i), (A(i+1) + A(i))/2)];
                endfor

  can be turned into the following one-liner:

                B = [diff(A)(:), 0.5*(A(1:end-1)+A(2:end))(:)]

  Note the usage of colon indexing to flatten an intermediate result into a column vector. This is a common vectorization trick.