Access Matrix Element in Mathematica

[Mindscrape]

[SOLVED] Access Matrix Element in Mathematica

Alright, so in Mathematica you define a matrix by saying A = {{a11,12,...},{21,a22,...}} for whatever matrix you are making. How do you access a particular element of that matrix?

Argh, Matlab is so much better.

 

[ozymandias]

Yep, Mathematica is the crappiest language I've ever come across, and I've worked with more than a few. :)

Use Extract, e.g.:

Extract[Extract[A,1],2] = a12

If possible, use IDL, Matlab, R, Octave, SciLab, Python with NumPy and SciPy or anything else. I'd rather use an abacus than use Mathematica :). Good luck with your work.

--------
Assaf
http://www.physicallyincorrect.com/"

 

[Hurkyl]

If I recall correctly, L[[x]] extracts the x-th element of a list.

If you really don't want to type A[[x]][[y]], you can always define a function:

A[x_, y_] := A[[x]][[y]]

and then you should be able to use A[x, y] to index your matrix. (I think you can use the same letter A for both these purposes. If it fails or you find it confusing, then just rename the function to something else.

You could even do a generic

Get[A_, x_, y_] := A[[x]][[y]]

that takes the matrix as an argument. Then you'd call

Get[A, x, y]



Matlab was designed for the sole purpose of manipulating matrices -- therefore it should be no surprise that it's more convenient to use Matlab instead of Mathematica for manipulating matrices.

Mathematica isn't a bad language: the catch is that it's a functional language, which takes a bit of adjustment if you've never programmed in a functional language before.

 

[ozymandias]

I guess it's a matter of taste. But I have worked with LISP & Haskell. Can't say they've changed my opinion about Mathematica

--------
Assaf
http://www.physicallyincorrect.com/"

 

[Mindscrape]

Got it. Thanks guys, I would have never sorted through mathematica help well enough to figure this out.

 

[Mormegil]

It really isn't that difficult - you can use Part[A, i, j]=aij