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I've got data of the type:

list = {"Class","MW","10 - 11"}

which I would like to split into a number of lists based on the number of characters in the second list element. In the above case, the desired output would be:

newlists = {{"Class","M","10-11"},{"Class","W","10-11"}}

StringSplit[list[[2]],""] gets me in the right direction (the string I want to split will always be in the same position in the list); however, I don't know how to thread this new sublist through the original list.

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    $\begingroup$ Guessing where you're going with this, you might want to look at Generating schedules/timetables in Mathematica $\endgroup$
    – rm -rf ♦
    Commented Oct 2, 2013 at 15:56
  • $\begingroup$ @rm-rf Wish I had posted this question before writing the grid layout code... $\endgroup$
    – bobthechemist
    Commented Oct 2, 2013 at 17:50
  • $\begingroup$ did I really write one of those answers? sloppy stuff... :) $\endgroup$
    – cormullion
    Commented Oct 2, 2013 at 19:27
  • $\begingroup$ @cormullion I found it ironic that a 10k+ rep'er was referring to others as 'experts'. I wonder if SE gives us a way to see what the rep was when a person answered the question. $\endgroup$
    – bobthechemist
    Commented Oct 2, 2013 at 19:59
  • 1
    $\begingroup$ @bobthechemist You can find a user's network profile from their site profile. From there, the reputation tab has a nice plot that you can use to quickly find out what the user's rep was on a given date. $\endgroup$
    – rm -rf ♦
    Commented Oct 2, 2013 at 20:24

5 Answers 5

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Here's how you can thread them:

newlists = Thread[{#, Characters@#2, ##3}] & @@ list
(* {{"Class", "M", "10 - 11"}, {"Class", "W", "10 - 11"}} *)
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  • $\begingroup$ Is there a less ambiguous way to map this command over a list of list: Thread[{#, Characters@#2, ##3}]& @@ # & /@ multilists? I don't know how concerned I should be about nested pure functions. $\endgroup$
    – bobthechemist
    Commented Oct 2, 2013 at 18:02
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    $\begingroup$ @bobthechemist Thread[{#, Characters@#2, ##3}] & @@@ multilists you can also add // Flatten[#, 1] & if you need. $\endgroup$
    – Kuba
    Commented Oct 2, 2013 at 19:08
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Here is an approach that doesn't use threading.

data = {"Class", "MW", "10 - 11"};
{a, b, c} = data;
new = {a, #, c} & /@ Characters @ b

{{"Class", "M", "10 - 11"}, {"Class", "W", "10 - 11"}}
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Distribute[MapAt[Characters, list, {2}], List] (* or *)
Distribute[MapAt[StringSplit[#, ""]&, list, {2}], List]

{{"Class", "M", "10 - 11"}, {"Class", "W", "10 - 11"}}

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Maybe not handy but interesting way to apply automatic threading:

SetAttributes[h, Listable];
h @@ MapAt[Characters, list, {2}] /. h -> List

{{"Class", "M", "10 - 11"}, {"Class", "W", "10 - 11"}}

multilist = {{"Class", "MW", "10 - 11"}, {"Class", "MK", "10 - 11"}}

h @@@ MapAt[Characters, multilist, {All, 2}] /. h -> List

{{{"Class", "M", "10 - 11"}, {"Class", "W", "10 - 11"}}, 
   {{"Class", "M", "10 - 11"}, {"Class", "K", "10 - 11"}}}
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fun[u_] := Module[{dow},
  dow = Characters[#[[2]]] &@u;
  ReplacePart[u, 2 -> #] & /@ dow]
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