Qurak

Get parts of a matrix

Workflow 7 steps, run in order in one session. Every step was executed against the engine and the output below is what it produced.

Step 1
mat = Table[Subscript[m, i, j], {i, 5}, {j, 5}]
Output
{{Subscript[m, 1, 1], Subscript[m, 1, 2], Subscript[m, 1, 3], Subscript[m, 1, 4], Subscript[m, 1, 5]}, {Subscript[m, 2, 1], Subscript[m, 2, 2], Subscript[m, 2, 3], Subscript[m, 2, 4], Subscript[m, 2, 5]}, {Subscript[m, 3, 1], Subscript[m, 3, 2], Subscript[m, 3, 3], Subscript[m, 3, 4], Subscript[m, 3, 5]}, {Subscript[m, 4, 1], Subscript[m, 4, 2], Subscript[m, 4, 3], Subscript[m, 4, 4], Subscript[m, 4, 5]}, {Subscript[m, 5, 1], Subscript[m, 5, 2], Subscript[m, 5, 3], Subscript[m, 5, 4], Subscript[m, 5, 5]}}
Step 2
MatrixForm[mat]
Output
MatrixForm[{{Subscript[m, 1, 1], Subscript[m, 1, 2], Subscript[m, 1, 3], Subscript[m, 1, 4], Subscript[m, 1, 5]}, {Subscript[m, 2, 1], Subscript[m, 2, 2], Subscript[m, 2, 3], Subscript[m, 2, 4], Subscript[m, 2, 5]}, {Subscript[m, 3, 1], Subscript[m, 3, 2], Subscript[m, 3, 3], Subscript[m, 3, 4], Subscript[m, 3, 5]}, {Subscript[m, 4, 1], Subscript[m, 4, 2], Subscript[m, 4, 3], Subscript[m, 4, 4], Subscript[m, 4, 5]}, {Subscript[m, 5, 1], Subscript[m, 5, 2], Subscript[m, 5, 3], Subscript[m, 5, 4], Subscript[m, 5, 5]}}]
Step 3
Part[mat, 1, 2]
Output
Subscript[m, 1, 2]
Step 4
mat[[4]]
Output
{Subscript[m, 4, 1], Subscript[m, 4, 2], Subscript[m, 4, 3], Subscript[m, 4, 4], Subscript[m, 4, 5]}
Step 5
mat[[All, 4]]
Output
{Subscript[m, 1, 4], Subscript[m, 2, 4], Subscript[m, 3, 4], Subscript[m, 4, 4], Subscript[m, 5, 4]}
Step 6
mat[[1 ;; 2, 1 ;; 3]]//MatrixForm
Output
MatrixForm[{{Subscript[m, 1, 1], Subscript[m, 1, 2], Subscript[m, 1, 3]}, {Subscript[m, 2, 1], Subscript[m, 2, 2], Subscript[m, 2, 3]}}]
Step 7
mat[[2 ;; -2, 2 ;; -2]]//MatrixForm
Output
MatrixForm[{{Subscript[m, 2, 2], Subscript[m, 2, 3], Subscript[m, 2, 4]}, {Subscript[m, 3, 2], Subscript[m, 3, 3], Subscript[m, 3, 4]}, {Subscript[m, 4, 2], Subscript[m, 4, 3], Subscript[m, 4, 4]}}]

Functions used

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