Question

Say I have a string in a variable in MATLAB like the following:

this is the first line 
this is the second line 
this is the third line

I would like to add a fixed string at the beginning of each line. For example:

add_substring(input_string, 'add_this. ') 

would output:

add_this. this is the first line 
add_this. this is the second line 
add_this. this is the third line

I know I can do this by looping through the input string, but I am looking for a more compact (hopefully vectorized) way to do this, perhaps using one of MATLAB built-ins such as arrayfun accumarray.

Answer 1

The strcat function is what you’re looking for. It does vectorized concatenation of strings.

strs = {
    'this is the first line'
    'this is the second line'
    'this is the third line'
    }
strcat({'add_this. '}, strs)

With strcat, you need to put 'add_this. ' in a cell ({}) to protect it from having its trailing whitespace stripped, which is strcat’s normal behavior for char inputs.