How to get back name of the number from Max function?

Question

So I have this question, using a toy example:

a={1,"this"};
b={2,"that"};

result=Max[0,a[[1]],b[[1]]]

the result will be 2. However what I want to obtain is "that" (or at least "b"). How do I do this without making dozens of "If"s and conditionals??

a = {1, "this"}; b = {2, "that"}; #[[Ordering[#, -1, #[[1]] &]]] &@{a, b}? — Dr. belisarius, Dec 06 '13 at 20:43
Shorter a = {1, "this"}; b = {2, "that"}; #[[Ordering[#, -1]]] &@{a, b} — Dr. belisarius, Dec 06 '13 at 21:25
I have marked this as a duplicate. I feel that the subject is already well covered there. (And several other places.) Please review the answers there; if afterward you disagree vote or flag to reopen. — Mr.Wizard, Dec 06 '13 at 21:27
@belisarius If you disagree with the closure please vote to reopen. — Mr.Wizard, Dec 07 '13 at 01:37
@Mr.Wizard Nah, I posted my answer as a comment because I thought the question was surely covered somewhere else. The comment was just a rant. — Dr. belisarius, Dec 07 '13 at 01:46
@belisarius Okay. I agree that it would be good to be able to cast a normal vote but I suppose that could be seen as indecisiveness. — Mr.Wizard, Dec 07 '13 at 01:48
Please don't use the same post to ask more questions. Use a new post instead. — Sjoerd C. de Vries, Dec 07 '13 at 22:53
ok, do I do it now, or just leave it like this (and take the advice for the future)? — Strumillo, Dec 07 '13 at 22:55
Please do it now. I voted to keep this closed to encourage you to remove your edit and post it as a separate question. — m_goldberg, Dec 07 '13 at 23:22

score 6 · Answer 1 · answered Dec 06 '13 at 21:09

6

If you have Mathematica on the Raspberry Pi (or Mathematica 10), you could use Association to store your data, which allows you to do these operations easily:

With[{a = <|1 -> "this", 2 -> "that"|>},
    a@Max@Keys@a
]
(* that *)

You can convert your list to an association as: Association @@ Rule @@@ {a, b}

answered Dec 06 '13 at 21:09

rm -rf

88,781
21
293
472

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Show a screen capture, or it didn't happen – Dr. belisarius Dec 06 '13 at 21:15
@belisarius Now vote! :D – rm -rf Dec 06 '13 at 21:16
Ok, Ok, you have it :) – Dr. belisarius Dec 06 '13 at 21:19

score 0 · Answer 2 · answered Dec 06 '13 at 20:42

0

a={1,"this"};
b={2,"that"};

Max[0, a[[1]], b[[1]]] /. Rule @@@ {a, b}

This gives :

that

answered Dec 06 '13 at 20:42

andre314

18,474
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wooooooow, thank you! – Strumillo Dec 06 '13 at 20:57
can I ask one more thing? how do I get whole b back? I'm just mesmerized by 3 @@@ and how it works:) – Strumillo Dec 06 '13 at 20:59
To obtain {2,"that"} instead of "that", you can do Max[0, a[[1]], b[[1]]] /. ((#[[1]] -> #) & /@ {a, b}) – andre314 Dec 06 '13 at 21:04

score 0 · Answer 3 · answered Dec 06 '13 at 21:13

0

a={1,"this"};
b={2,"that"};

Cases[{a, b}, {key_, value_} /; (key == Max[{a, b}[[All, 1]]])]

or

Select[{a, b}, (#[[1]] == Max[{a, b}[[All, 1]]] &)]

For variety's sake. Likely not the way to go for long lists though.

answered Dec 06 '13 at 21:13

chuy

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How to get back name of the number from Max function?

3 Answers3