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Wolfram Language equivalent to Matlab Rot90?

Paul Davidson

Posted 8 years ago

Does anyone know if there is there a wolfram equivalent for the Matlab command Rot90 ? B = rot90(A) rotates array A counterclockwise by 90 degrees. For multidimensional arrays, rot90 rotates in the plane formed by the first and second dimensions. B = rot90(A,k) rotates array A counterclockwise by k*90 degrees, where k is an integer.

POSTED BY: Paul Davidson

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Sander Huisman

Sander Huisman, University of Twente

Posted 8 years ago

Other possibilities are: rotcw2 = Reverse/Transpose; rotccw2 = Transpose/Reverse; rotcw3[x_]:=Transpose[Reverse[x]] rotccw3[x_]:= Reverse[Transpose[x]] rotcw4 = Transpose[Reverse[#]]& rotccw4 = Reverse[Transpose[#]]& rotcw5 = (Reverse /@ Transpose[#])& rotccw5 = (Transpose[Reverse /@ #])& Or using Table: Table[a[[dimx - j + 1, i]], {i, dimy}, {j, dimx}] // MatrixForm Table[a[[j, dimy - i + 1]], {i, dimy}, {j, dimx}] // MatrixForm You can probably also use SparseArray or MapIndexed... There are many many ways of doing this, it just depends on what you feel most comfortable using... @* or /* or /@ or #...& might seem intimidating for some people...

Other possibilities are:

rotcw2 = Reverse/*Transpose;
rotccw2 = Transpose/*Reverse;

rotcw3[x_]:=Transpose[Reverse[x]]
rotccw3[x_]:= Reverse[Transpose[x]]

rotcw4 = Transpose[Reverse[#]]&
rotccw4 = Reverse[Transpose[#]]&

rotcw5 = (Reverse /@ Transpose[#])&
rotccw5 = (Transpose[Reverse /@ #])&

Or using Table:

Table[a[[dimx - j + 1, i]], {i, dimy}, {j, dimx}] // MatrixForm   
Table[a[[j, dimy - i + 1]], {i, dimy}, {j, dimx}] // MatrixForm

You can probably also use SparseArray or MapIndexed... There are many many ways of doing this, it just depends on what you feel most comfortable using... @* or /* or /@ or #...& might seem intimidating for some people...

POSTED BY: Sander Huisman

Paul Davidson

Posted 8 years ago

Thank you evryone for your comments but special thanks to Sander for such a simple solution.

POSTED BY: Paul Davidson

Sander Huisman

Sander Huisman, University of Twente

Posted 8 years ago

This is not what the OP asks for. Rot90 'rotates' a matrix in 90 degree steps (http://fr.mathworks.com/help/matlab/ref/rot90.html). Not rotation like Rotate, RotationTransform, RotationMatrix.

POSTED BY: Sander Huisman

Sander Huisman

Sander Huisman, University of Twente

Posted 8 years ago

As David said it is very easy to do so: rotccw = Reverse@Transpose; ( defines a function to do counterclockwise rotation ) rotcw = Transpose@Reverse; (* and clockwise rotation *) a = Partition[Range[16], 4]; MatrixForm[a] MatrixForm[rotcw[a]] MatrixForm[rotccw[a]]

As David said it is very easy to do so:

rotccw = Reverse@*Transpose; (* defines a function to do counterclockwise rotation *)
rotcw = Transpose@*Reverse;  (* and clockwise rotation *)

a = Partition[Range[16], 4];
MatrixForm[a]
MatrixForm[rotcw[a]]
MatrixForm[rotccw[a]]

POSTED BY: Sander Huisman