I’m trying to fill this matrix

=========================================== 
F (Rows: 8 Cols: 4)
===========================================
[[-1, -1, -1, -1]
 [-1, -1, -1, -1]
 [-1, -1, -1, -1]
 [-1, -1, -1, -1]
 [-1, -1, -1, -1]
 [-1, -1, -1, -1]
 [-1, -1, -1, -1]
 [-1, -1, -1, -1]]
===========================================

with this one:

===========================================
MR (Rows: 3 Cols: 1)
===========================================
[[1]
 [3]
 [0]]
===========================================

by substituing values with block operation

F.block(1, MR.size(), 3, 0) = MR;

But I get an error

Assertion failed: (startRow >= 0 && blockRows >= 0 && startRow <= xpr.rows() - blockRows && startCol >= 0 && blockCols >= 0 && startCol <= xpr.cols() - blockCols), function Block,

What’s wrong? Thank you