# Matrix _ List -- select columns

## Synopsis

• Operator: _
• Usage:
f_cols
• Inputs:
• f, , a matrix between free modules
• cols, a list, a list of integers denoting the choice of columns
• Outputs:
• , the submatrix of f corresponding to the columns cols.

## Description

This is the same as calling submatrix(f,cols).
 i1 : R = QQ[a..f]; i2 : p = matrix {{a,b,c},{d,e,f}} o2 = | a b c | | d e f | 2 3 o2 : Matrix R <--- R i3 : p_{1} o3 = | b | | e | 2 1 o3 : Matrix R <--- R i4 : p_{1,2,0} o4 = | b c a | | e f d | 2 3 o4 : Matrix R <--- R