How to | Get Parts of a Matrix
Mathematica has many matrix operations that support operations such as building, computing, and visualizing matrices. It also has a rich language for picking out and extracting parts of matrices.
Define the following matrix. Note how a matrix in Mathematica is not restricted to number entries:
Out[268]//MatrixForm= |
| |  |
Use Part to go to the first row and take the second element:
| Out[269]= |  |
Or use the shorthand notation 
for Part:
| Out[270]= |  |
To take an entire row, use one index to specify the row:
| Out[271]= |  |
To take an entire column, you need to select all rows with All and specify the column:
| Out[272]= |  |
To pick out a submatrix, you can use Span (
). First, define a 4×5 matrix:
Out[274]//MatrixForm= |
| |  |
The top-left 3×4 matrix with bold entries here corresponds to rows 1 through 3 and columns 1 through 4:
Extract the highlighted matrix by using Span (
) to specify the relevant span of rows and columns:
| Out[275]= |  |
Out[276]//MatrixForm= |
| |  |
Extract all elements except the outermost rows and columns (negative indices count from the end):
| Out[277]= |  |
Out[278]//MatrixForm= |
| |  |
