Question

I have a MATLAB matrix, that is 1000×4, to use as an input for a function. I need to add a new column that contains a certain string. So how can I make a new column where all the values are ‘TEST’?

Answer 1

Since it’s a little unclear what you want, here are some options:

• To make a 1000-by-4 matrix where each row is 'TEST', you can use the function REPMAT:

  M = repmat('TEST',1000,1);
  

• To add 'TEST' to the end of each row of a 1000-by-4 matrix of characters, you can use the function STRCAT:

  M = repmat('a',1000,4);  %# Sample matrix filled with 'a'
  M = strcat(M,'TEST');    %# Append 'TEST' to each row of M
  

• If your 1000-by-4 matrix is a numeric array instead of an array of characters, you will have to use cell arrays to combine the different types of data. Here’s one way you can do this:

  M = rand(1000,4);   %# A matrix of random numeric values
  M = num2cell(M,2);  %# Put each row of M in a cell, making
                      %#   a 1000-by-1 cell array
  M(:,2) = {'TEST'};  %# Add a second column to the cell array,
                      %#   where each cell contains 'TEST'