From b7add6b2b6edfc7a22d55675ff4edb5922f9a02d Mon Sep 17 00:00:00 2001
From: Anthony Scemama <scemama@irsamc.ups-tlse.fr>
Date: Wed, 16 Dec 2020 12:03:20 +0100
Subject: [PATCH] Added transpose

---
 linear_algebra/lib/matrix.ml  | 19 ++++++++++++++-----
 linear_algebra/lib/matrix.mli |  6 ++++++
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/linear_algebra/lib/matrix.ml b/linear_algebra/lib/matrix.ml
index b30c853..74095a3 100644
--- a/linear_algebra/lib/matrix.ml
+++ b/linear_algebra/lib/matrix.ml
@@ -68,12 +68,21 @@ let col_inplace t j =
   Mat.col t j
   |> Vector.of_bigarray_inplace
 
-(*
-let col t j =
-  Mat.col t j
-  |> Vector.of_bigarray
-*)
+let transpose t =
+  Mat.transpose_copy t
 
+let transpose_inplace t =
+  let mat = to_bigarray_inplace t in
+  let d1 = dim1 t in
+  let d2 = dim2 t in
+  assert (d1 = d2);
+  for j=1 to d1 do
+    for i=1 to (j-1) do
+      let ij, ji = mat.{i,j}, mat.{j,i} in
+      mat.{i,j} <- ji;
+      mat.{j,i} <- ij
+    done;
+  done
 
 let to_col_vecs t =
   Mat.to_col_vecs t
diff --git a/linear_algebra/lib/matrix.mli b/linear_algebra/lib/matrix.mli
index c99c0f8..46f3090 100644
--- a/linear_algebra/lib/matrix.mli
+++ b/linear_algebra/lib/matrix.mli
@@ -129,6 +129,12 @@ val col: ('a,'b) t -> int -> 'a Vector.t
 val col_inplace: ('a,'b) t -> int -> 'a Vector.t
 (** Returns a column of the matrix as a vector *)
 
+val transpose: ('a,'b) t -> ('b,'a) t
+(** Returns the transposed matrix *)
+
+val transpose_inplace: ('a,'a) t -> unit
+(** Transposes the matrix in place. *)
+
 val detri: ('a,'b) t -> ('a,'b) t 
 (** Takes an upper-triangular matrix, and makes it a symmetric matrix
 by mirroring the defined triangle along the diagonal. *)