MatSetValue

Set a single entry into a matrix.

PetscErrorCode MatSetValue(Mat m,PetscInt row,PetscInt col,PetscScalar value,InsertMode mode);

Not collective

	m	- the matrix
	row	- the row location of the entry
	col	- the column location of the entry
	value	- the value to insert
	mode	- either INSERT_VALUES or ADD_VALUES

For efficiency one should use MatSetValues() and set several or many values simultaneously if possible.