Reshape vectors exactly like in MATLAB

Question

This gives a 64×1 column vector in Mathematica:

F := Flatten[ArrayFlatten[
ArrayFlatten[
 Table[Subscript[f, i, j, k, l, m, 
  n], {i, 0, 1}, {l, 0, 1}, {j, 0, 1}, {m, 0, 1}, {k, 0, 1}, {n, 
   0, 1}]]]] // MatrixForm

as F=(1:64)' does in MATLAB.

In MATLAB, reshape(F,16,4) gives a 16×4 matrix, where column 1 is the first 16 elements of F, column 2 the 17th to 32nd, etc.

In Mathematica, the best equivalents for reshaping seem to be the top two answers here.

But when I apply either of these commands, I do not get a 16×4 matrix that's constructed like reshape in MATLAB. Instead I get a 16×4 matrix where row 1 is the first four elements of F, etc.

I have tried adding transpose operations in every location imaginable, and still can't get my Mathematica output to match the MATLAB. I've also tried wrapping List[] around the definition of F to make F appear like a row instead of a column, but everything I do seems to not work.

Any help is much appreciated!

Answer 1

Just apply transpose to the top answer:

reshape[mtx_, n_, _] := Transpose[Partition[Flatten[mtx], n]];

Answer 2

You might also use the (undocumented) function Internal`Deflatten[] for the purpose:

reshape[arr_List, dims : {__Integer}] :=
   Transpose[Internal`Deflatten[Flatten[arr], Reverse[dims]]]

reshape[Range[16*4], {16, 4}]
   {{1, 17, 33, 49}, {2, 18, 34, 50}, {3, 19, 35, 51}, {4, 20, 36, 52},
    {5, 21, 37, 53}, {6, 22, 38, 54}, {7, 23, 39, 55}, {8, 24, 40, 56},
    {9, 25, 41, 57}, {10, 26, 42, 58}, {11, 27, 43, 59}, {12, 28, 44, 60},
    {13, 29, 45, 61}, {14, 30, 46, 62}, {15, 31, 47, 63}, {16, 32, 48, 64}}

Answer 3

Since Deflatten isn't in version 7 here is my proposal:

reshape[a_, d__] := Fold[Partition, a, Reverse@{d}] ~Flatten~ {1, 3}

Which could also be written:

reshape[a_, r___, p_] := reshape[a ~Partition~ p, r]

reshape[a_] := a ~Flatten~ {1, 3}

Test:

reshape[Range@24, 3, 8] // MatrixForm

reshape[Range@24, 3, 4, 2] // MatrixForm

reshape[Range@24, 6, 2, 2] // MatrixForm