How can you convert a matrix back into a list of lists?

Question

It is very simple in Mathematica to convert a list of lists into a matrix: all you need to do is apply the //MatrixForm function to it and voila.

Is it possible to do the reverse though? I have a matrix that I want to convert back into a list of lists, so as to manipulate its elements more easily. Is this possible? Is there a 'ListForm' function that deletes all MatrixForms from the element in question?

As an example, here is the FullForm for one of my elements: MatrixForm[List[List[63],List[4,62]]]

Is there a function which would take this as input and return simply List[List[63],List[4,62]]?

Thank you

You should go through this section of the documentation. The things covered there are essential for using Mathematica, and will also answer your question. — Szabolcs, Mar 02 '14 at 14:53
possible duplicate of Why does MatrixForm affect calculations? — Simon Woods, Mar 02 '14 at 14:57
another approach to maintaining your underlying data structure but still using MatrixForm for display is to enclose in brackets ()s e.g. (x={{1,2,3},{4,5,6}})//MatrixForm. — PlaysDice, Mar 02 '14 at 21:54

score 13 · Accepted Answer · edited Apr 13 '17 at 12:55

13

I'll start with the standard warning: MatrixForm is just a wrapper that makes your matrices look pretty. Nothing more, nothing less. It does not "convert" a list of lists to a matrix. Your list of lists is already a matrix:

m = Identity@10;
MatrixQ@m
(* True *)

Using MatrixForm wrapped matrices in calculations will only give you an error. Use it only for typesetting/display purposes.

To answer your specific question, if you have a MatrixForm wrapped around it for whatever reason, you can remove the wrapper in one of the following ways:

First@m (* or *)
Identity @@ m (* or *)
m /. MatrixForm[x_] :> x

which will give you back the list of lists.

edited Apr 13 '17 at 12:55

Community

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answered Mar 02 '14 at 14:23

rm -rf

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Why not First? – Szabolcs Mar 02 '14 at 14:48
@Szabolcs Heh, why not indeed! :) I'll add it in. – rm -rf Mar 02 '14 at 14:51
2

While we´re at it, why not m[[1]]? – Yves Klett Mar 02 '14 at 18:09

How can you convert a matrix back into a list of lists?

1 Answers1