List manipulations with ; and ;;

Asked Feb 13 '15 at 14:14

Active Feb 13 '15 at 14:21

Viewed 68 times

I have the following list:

L = {{a1,a2,a3,a4},{b1,b2,b3,b4},{c1,c2,c3,c4}}

By using just the ; or ;; "iterators", or equivalent, how can I extract a list from L such that:

NewL = {{a1,a3},{b1,b3},{c1,c3}}

Up today I haven't understand exactly how to work with these list manipulation techniques. I know that m;;n means "partis m trough n", but at which level? And what does ; alone stands for? Or the comma ,?

edited Feb 13 '15 at 14:21

Szabolcs

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asked Feb 13 '15 at 14:14

Miguel

2

L[[All, {1,3}]]. Take a look at Part and Span documentation. Moreover, single ; is something different. – Kuba Feb 13 '15 at 14:15
3

or L[[;; , 1 ;; ;; 2]] – paw Feb 13 '15 at 14:20
Ok, thank you very much! – Miguel Feb 13 '15 at 14:21
1

It looks like the question will be closed soon. After reading the documentation on Part and Span, do you still have questions? – Szabolcs Feb 13 '15 at 17:12

List manipulations with ; and ;;

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