How to insert a column into a matrix, the correct Mathematica way

Question

I think Mathematica is biased towards rows not columns.

Given a matrix, to insert a row seems to be easy, just use Insert[]

(a = {{1, 2, 3},         


        

Answer 1

I originally posted this as a comment (now deleted)

Based on a method given by user656058 in this question (Mathematica 'Append To' Function Problem) and the reply of Mr Wizard, the following alternative method of adding a column to a matrix, using Table and Insert, may be gleaned:

(a = {{1, 2, 3}, {4, 0, 8}, {7, 8, 0}});
column = {97, 98, 99};

Table[Insert[a[[i]], column[[i]], 2], {i, 3}] // MatrixForm

giving

Similarly, to add a column of zeros (say):

Table[Insert[#[[i]], 0, 2], {i, Dimensions[#][[1]]}] & @ a 

As noted in the comments above, Janus has drawn attention to the 'trick' of adding a column of zeros by the ArrayFlatten method (see here)

ArrayFlatten[{{Take[#, All, 1], 0, Take[#, All, -2]}}] & @ 
  a // MatrixForm

Edit

Perhaps simpler, at least for smaller matrices

(Insert[a[[#]], column[[#]], 2] & /@ Range[3]) // MatrixForm

or, to insert a column of zeros

Insert[a[[#]], 0, 2] & /@ Range[3]

Or, a little more generally:

Flatten@Insert[a[[#]], {0, 0}, 2] & /@ Range[3] // MatrixForm

May also easily be adapted to work with Append and Prepend, of course.