compare two rows of a matrix

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Basically, I want to compare two rows from a matrix and return the logic values.

 Mat x(240, 320, CV_32F); // 240*320 image size
 Mat pairs(5, 2, CV_8U);  // 5*2 matrix, each row is a pair of row index from x
 int P  = pairs.rows;
 for (int j=0; j<P; j++) {
 z = (x.row(pairs(j,1)) > x.row(pairs(j,2)));
 }

It gives the following error,

   error C2664: 'cv::Mat cv::Mat::operator ()(const cv::Range *) const' : cannot convert parameter 1 from 'int' to 'const cv::Range *'

How to resolve this issue? Is it because the operator of row(int i) is wrong?

Thanks for your help.