Dropping the 3rd variable in a list of lists

Question

I have the following text: loadeddata={{1,2,3},{5,2,1},{1,4,1},{1,5,0},{2,3,5}}

How can I removed the third numbers in each of the sublists?

The real data has 600 of these sublists. I want to use Histogram3D with the first two variables.

If you like to use a pattern then loadeddata /. {a_, b_, c_} -> {a, b} — bobbym, Sep 26 '16 at 05:32

score 4 · Accepted Answer · answered Sep 26 '16 at 03:40

4

Here's a convenience function for you:

DropColumn[mat_, n_] := Module[
    {toDrop, toKeep, numberOfColumns, normalized, fixNegs},
    numberOfColumns = Length[mat[[1]]];
    fixNegs = Function[If[Less[#, 0], numberOfColumns + # + 1, #]];
    toDrop = If[ListQ[n], Map[fixNegs, n], {fixNegs @ n}];
    toKeep = Complement[Range @ numberOfColumns, toDrop];
    Return[mat[[All, toKeep]]]
   ];

Here's how you use it:

loadeddata = {{1, 2, 3}, {5, 2, 1}, {1, 4, 1}, {1, 5, 0}, {2, 3, 5}};
loadeddata = DropColumn[loadeddata, 3]

answered Sep 26 '16 at 03:40

M.R.

31,425
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Can you explain what advantage it has over loadeddata[[All, 1 ;; 2]]? – Kuba Sep 26 '16 at 09:22
Let's you specify the columns you want to delete as opposed to the columns you don't? – M.R. Sep 26 '16 at 14:31
I see, makes sense. If you disagree with closing you can vote to reopen. – Kuba Sep 26 '16 at 14:45

Dropping the 3rd variable in a list of lists

1 Answers1