Store a value in an element outside of the matrix (as in Matlab)

Asked Apr 28 '18 at 09:56

Active Apr 28 '18 at 09:56

Viewed 19 times

Suppose that I have the matrix

A = {{8, 1, 6}, {3, 5, 7}, {4, 9, 2}};

In Matlab/Octave one may store a value in an element outside of the matrix whose size increases to accommodate the newcomer:

>> A = magic(3);
>> A(4,5) = 17;
>> A

A =

     8     1     6     0     0
     3     5     7     0     0
     4     9     2     0     0
     0     0     0     0    17

How is possible to achieve a similar behavior in Mathematica?

asked Apr 28 '18 at 09:56

Dimitris

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There is no direct way to do this in Mathematica. Not build in. Must write some code. Also see this how-to-expand-the-size-of-the-matrix-automatically – Nasser Apr 28 '18 at 10:10
@Nasser: Thanks! – Dimitris Apr 28 '18 at 10:13
This can be done with ArrayRules and SparseArray or with ArrayPad (or other padding functions.) Which solution to use depends on what size of matrices you are going to deal with. Also, this way of increasing dense matrices might be seen as a bad practice from certain viewpoints. – Anton Antonov Apr 28 '18 at 10:21
@AntonAntonov Thanks a lot. The suggested link contains a relevant comment. – Dimitris Apr 28 '18 at 10:33

Store a value in an element outside of the matrix (as in Matlab)

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