Get only the digits in the first 2 characters of a string

Hello,

I'm trying to find the numbers of a list of file names. Each file name starts with a variable numbers between 1 and 15:

filename1 = '13_data_rec_233';
filename2 = '1_data_rec_124';

I need to store the number of each file (digits before the underscore) for later use. In this case I can't cimply get the first two chracters as for filename2 it would get '1_'

Any suggestion on how to proceed?

Answer 1

[Jan]

filename1 = '13_data_rec_233';
filename2 = '1_data_rec_124';

num1 = sscanf(filename1, '%d', 1)
num2 = sscanf(filename2, '%d', 1)

Or do you want the number as char vector?

num1 = strtok(filename1, '_')
num2 = strtok(filename2, '_')

If there is no separator as "_" in your case, this can help:

filename1 = '13data_rec_233';  % Could be '13value_rec_233' also
filename2 = '1data_rec_124';   % Could be '1value_rec_124' also
num1 = FirstNumber(filename1)
num2 = FirstNumber(filename2)

function T = FirstNumber(S)
alpha = ~strprop(S, 'digit');
T     = S(1:find(alpha, 1));
end

If the numerical value is needed, use sscanf() as above.

Of course regexp is working also, but its bigger power leads to slower run times.

[MDias]

Thanks Jan!

sscanf is what I need.