say I have a 2 dimensionsal array like
a={{1,2,3},{4,5,6},{7,8,9}}
and a vector like
v={10,11,12}
I want the result to be
{{{10,1},{10,2},{10,3}},{{11,4},{11,5},{11,6}},{{12,7},{12,8},{12,9}}}
What command should I use? Thank you for suggestions. regards, hal.
There is probably a better solution, but this should work.
Example:
a={{1,2,3},{4,5,6},{7,8,9}}
v={10,11,12}
Thread[List[v[[#]], a[[#]]]] & /@ Range @ Length @ v
Alternative:
MapThread[Thread[{##}] &, {v, a}]
Output:
(*{{{10, 1}, {10, 2}, {10, 3}}, {{11, 4}, {11, 5}, {11, 6}}, {{12,
7}, {12, 8}, {12, 9}}}*)
Here's a quick way to get there,
Thread /@ Transpose@{v, a}
(* {{{10, 1}, {10, 2}, {10, 3}}, {{11, 4}, {11, 5}, {11,
6}}, {{12, 7}, {12, 8}, {12, 9}}} *)
The point here is that Transpose@{v, a} gives {{10, {1, 2, 3}}, {11, {4, 5, 6}}, {12, {7, 8, 9}}}, and you can use Thread on the individual elements.
You can achieve the desired result in many ways with Mathematica. Just some variants in addition:
MapThread[Thread[{##}] &, {v, a}]
Inner[Thread[{#1, #2}] &, v, a, List]
g[x_, y_] := Prepend[{#}, y] & /@ x;
h[x_, y_] := {y, #} & /@ x;
t = Thread[{a, v}];
g @@@ t
h @@@ t
MapThread[Map[t \[Function] {#1, t}, #2] &, {v, a}]
