Writing lines to .csv file fails with command fprintf - matlab

Question

I want to acces a .csv file, look for empty data blocks and store all of the lines that have no empty data blocks.
This is my code:
filename = 'C:\Users\try.csv';
file1 = fopen(filename); %Acces file with empty data blocks
filename2 = 'C:\Users\try_corrected.csv';
file2 = fopen(filename2); %Acces destination file
tline = fgets(file1); %Read the first line of file1
while ischar(tline)
detected = false;
[r,s] = size(tline); %Determine the lengt of the textline for the for-loop
for(i=1: 1: s)
if( (tline(i)==',' && tline(i+1) ==',') || tline(1)==',' || tline(s-2)==',' )
detected = true %Line should not be printed in destination file
break;
end
end
if detected == false
fprintf(file2,'%s\n',tline);
end
tline = fgets(file1);
end
type 'C:\Users\try_corrected.csv'
fclose(file2);
textdata = textscan(file1, '%s %f %f %f %s %f %f %f %s %f %s','HeaderLines', 1,'Delimiter',',');
fclose(file1);
If I do the "type" command, I should see all the printed strings which is not the case.
Am I using fprintf wrong? I know there is a command called csvwrite but I thought this could work too?

Answer 1

First, when you open your destination file you need to open it for writing. Without a second parameter fopen will open for read access. If your destination file did not exist it would return you a -1 file handle.
Use instead:
fopen(filename2,'w')
Here is a simplified version of your code including that amendment:
filename = 'c:\try.csv';
fid_in = fopen(filename,'r'); %Access file with empty data blocks
filename2 = 'C:\try_corrected.csv';
fid_out = fopen(filename2,'w'); %Access destination file
while (~feof(fid_in))
str=fgets(fid_in);
if (~doublecommas(str))
fprintf(fid_out,'%s',str);
end
end
fclose(fid_in);
fclose(fid_out);
type(filename2)
This uses a different method to detect double presence of commas in the CSV line:
function flag=doublecommas(str)
flag=false; % flag = result returned,
% true if empty CSV fields present in line
if (ischar(str) && length(str)>0)
for cindex=1:length(str)-1
if strcmp(str(cindex:(cindex+1)),',,')
flag=true; break;
end
end
end
return;