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Define a big matrix in Sage

asked 2016-02-06 13:47:22 -0600

Dianbin Bao gravatar image

updated 2016-02-07 07:54:27 -0600

Hi all,

I would like to define a big matrix E (130$\times$ 30) with entries being a list like E[11,1] = [x, [1,-2]];

E[14,1] = [x, [1,-1,-2,1]]; or 0. These entries are stored in a separate file which is readable by Pari but not Sage.

How do I define it by Sage?

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Can you make the info a dictionary, which is an easy way to define the matrix?

kcrisman gravatar imagekcrisman ( 2016-02-06 17:46:36 -0600 )edit

To people who has similar problems: One can unravel multidimensional list to one dimensional list and then input Sage.

Dianbin Bao gravatar imageDianbin Bao ( 2016-02-11 09:48:26 -0600 )edit

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answered 2016-02-08 08:00:42 -0600

vdelecroix gravatar image

updated 2016-02-08 08:01:07 -0600

A Sage matrix must have its entries being element of some ring. In other words you can not have a matrix of lists. However it is perfectly fine to have a 2d array (aka a "list of lists").

sage: l = [[1, [2,3]], [2, [5,4]]]
sage: print l
[[1, [2, 3]], [2, [5, 4]]]

To execute some code contained in a string you might use the "eval" or "sage_eval" command

sage: my_string = "[[1, [2,3]], [2, [5,4]]]"
sage: sage_eval(my_string)   # run the Python code from my_string
[[1, [2, 3]], [2, [5, 4]]]

And to read the content of the file these are the standard Python commands open/close

sage: f = open("")   # open the file
sage: string =          # read what is inside (result is a string)
sage: f.close()                  # close the file
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Asked: 2016-02-06 13:47:22 -0600

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Last updated: Feb 08 '16