# Delete rows from 3D matrix and convert it to 2D matrix

I have a 3d matrix of dimension $$11 \times 1000 \times 3$$. I need to remove the first 10 rows from all 2D matrix so that the output is $$11 \times 990 \times 3$$. After that I need to convert it into a 2d matrix such that the dimension becomes $$10890\times3$$.

• Look at Part for selecting pieces of the matrix and ArrayReshape for reshaping. Jul 7 at 10:39

As suggested in the comment, you should use Part and ArrayReshape:

(* Create random 3D matrix with dimensions 11 x 1000 x 3 *)
mat = RandomReal[1, {11, 1000, 3}];
Dimensions[mat]
(* {11, 1000, 3} *)

mat2 = mat[[All, 11 ;;, All]];
Dimensions[mat2]
(* {11, 990, 3} *)

mat3 = ArrayFlatten[mat2, 1];
Dimensions[mat3]
(* {10890, 3} *)