how can one write the code below in more compact and faster way?

Code: Select all

const int sz=10;
VectorXd v = VectorXd::Random(sz);
 VectorXd vdiff(v.size()-1);
 for(int j=0; j<vdiff.size(); ++j)
  { vdiff(j)=v(j+1)-v(j);  }

int n = v.size();
vdiff = v.head(n-1) - v.tail(n-1);

and for a matrix:
int n = mat.rows(), m=mat.cols();
mdiff = mat.topLeftCorner(n-1,m-1) - mat.bottomRightCorner(n-1,m-1);

Only small correction:
for vectors one should switch tail and head in order to get the result as described in the first post
vdiff = v.tail(n-1) - v.head(n-1);