Where is the Documentation for Indexing on the Left Hand Side of an Assignment?

5 visualizzazioni (ultimi 30 giorni)
I recently ran into something like this:
x = [1 2 3];
x([1 2 1]) = [10 20 30]
x = 1×3
30 20 3
So it looks like the second index of 1 on the LHS takes precedence over the first. I hunted through the documentation (searching on "assignment" was particularly fruitless) and I couldn't find any documentation discussing how indexing works on the LHS of an assignment in general, much less the rule for this particular use case.
Can anyone link to relevant doc page(s)? I feel like I've seen this topic in the doc before, but for the life of me can't find it now.
  2 Commenti
Chris
Chris il 12 Set 2022
Modificato: Bruno Luong il 12 Set 2022
I mean...
Slicing the array up with repeated elements makes sense on the right side, perhaps, but why would that happen on the left side? Matlab is probably just following the index order. Working through the array, it first sets x(1) to 10 (index 1), then ends by setting x(1) to 30 (index 3).
Paul
Paul il 12 Set 2022
Modificato: Paul il 12 Set 2022
Both of those links talk only about how data is extracted from an array with indexing in an expression. Neither talk about how data is assigned into an array with indexing. For me, "Matlab is probably" suggests it's worthy of being documented.
I don't know why that would happen on the LHS, but it's allowed so maybe there is some need/use for that feature.
Stephen's answer links to two blog posts that are exactly on point, so there must be some interest somewhere.

Accedi per commentare.

Risposta accettata

Stephen23
Stephen23 il 12 Set 2022
Modificato: Stephen23 il 12 Set 2022
  1 Commento
Paul
Paul il 12 Set 2022
Thanks for the links. However, I don't think blog posts are considered normative. IMO, the doc should cover indexing on the LHS (and I thought it did, at least in the past).

Accedi per commentare.

Più risposte (0)

Prodotti


Release

R2022a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by