Extracting element(s) of a matrix :

Input :

- To extract an element, put the matrix and then, beetween square
brackets put its row index, a comma, and its column index.
In
`Xcas`mode the first index is 0, in other modes the first index is 1.

Input :`[[3,4,5],[1,2,6]][0,1]``A[0,1]``A[0][1]``at(A,[0,1])``4` - To extract a row of the matrix
`A`, put the matrix and then, beetween square brackets put the row index, input :`[[3,4,5],[1,2,6]][0]``A[0]``at(A,0)``[3,4,2]` - To extract a part of a row, put two arguments
beetween the square brackets :
the row index and an interval to design the selected columns.

Input :`A[1,0..2]``[1,2,6]``A[1,1..2]``[2,6]` - To extract a column of the matrix
`A`, first tranpose`A`(`transpose(A)`) then extract the row like above.

Input :`tran(A)[1]``at(tran(A),1)``[4,2]` - To extract a part of a column of the matrix
`A`as a list, put two arguments beetween the square brackets : an index interval to design the selected rows and the column index.

Input :`A[0..0,1]``[4]`This may be used to extract a full column, by specifying all the rows as index interval.

Input :`A[0..1,1]``[4,2]` - To extract a sub-matrix of a matrix, put between the square brackets two
intervals : one interval for the selected rows and one interval for the
selected columns.

To definie the matrix`A`, input :`A:=[[3,4,5],[1,2,6]]``A[0..1,1..2]``[[4,5],[2,6]]``A[0..1,1..1]``[[4],[2]]`**Remark**If the second interval is omitted, the sub-matrix is made with the consecutive rows given by the first interval.

Input :`A[1..1]``[[1,2,6]]`

You may also assign an element of a matrix using the index notation,
if you assign with `:=` a new copy of the matrix is created
and the element is modified, if you assign with `=<`,
the matrix is modified in place.