Salem, I want to reduce the row of one matrix (attachment file). I want to use the Gauss method to will have one matrix like this : first line * * * *; second line 0 * * *; third line 0 0 * *; fourth line 0 0 0 *; I use the ReduceRow option, but the result is not good. The example is sent as an attachment of this post. I am waiting for your help. Greetings.
thank you for this response, I think that this is what I want to use, I will check it.
may be what you want is LUDecomposition
LUDecomposition
{lu, p, c} = LUDecomposition[H]; u = lu SparseArray[{i_, j_} /; j >= i -> 1, {4, 4}] // MatrixForm
