Face Recognition code use Jaffe data set

This is amit a new user of mat lab.... I'm doing face recognition project.....for which i have seen one code from GitHub

https://github.com/vipaerat/Facial-Expression-Detection

Code is fine and running ...

But I have one problem in code name file Preprocessor.m

From line 17 to 31 CODE

for i=1:no_files filename = files{i}; Im = imread(filename);

    hist = featureDetect(Im);

    trainX(i,:) = hist;

    if strcmp(type,'jaffe')~=0
        trainY(i,str2double(filename(13))+1) = 1;
    else
        trainY(i,str2double(filename(19))+1) = 1;
    end
    i
end

What is the meaning of that line its not run in my system...

• trainY(i,str2double(filename(13))+1) = 1;*

1. in my system filename(13) gives value 'a' which is not convert into double...

2. Why we are using 13 and 19 no for file....

3. How we divided the no of file into training and testing part....

PLEASE reply as soon as possible