You can load the elements of a matrix from an array:
Matrix A(3,2);
Real a[] = { 11,12,21,22,31,33 };
A << a;
This construction does not check that the numbers of elements match
correctly. This version of << can be used with submatrices on the left
hand side. It is not defined for band matrices.
Alternatively you can enter short lists using a sequence of numbers separated by << .
Matrix A(3,2);
A << 11 << 12
<< 21 << 22
<< 31 << 32;
This does check for the correct total number of entries, although the
message for there being insufficient numbers in the list may be delayed
until the end of the block or the next use of this construction. This
does not work for band matrices or submatrices, or for long lists. Also
try to restrict its use to numbers. You can include expressions, but
these must not call a function which includes the same construction.