How to continue in a loop when the file does not exist? - matlab

Question

This script download many files. However, I want the loop to continue when it doesn't find any file: File mot found.
for ii=1:length(t2)
d=t2(ii);
if year(d)>=2011
download(d)
end
end
Any ideas? Thanks

Answer 1

I'm guessing download is a function that downloads something from a server, so I don't see how exist will work. Either way, you can simply use a try catch block:
for ii=1:length(t2)
d=t2(ii);
if year(d)>=2011
try
download(d)
catch
end
end
end

Answer 2

You could add an 'if' statement before the download(d) statement to ask whether the file exists. Something like:
for ii=1:length(t2)
d=t2(ii);
if year(d)>=2011
if exist(d) % where d is the file
download(d)
else
continue % Jump to next loop iteration if file doesn't exist
end
end
end
Assuming that 'd' is the file in question that you want to download. You might need to use the file's whole address to make sure Matlab can find it.

Answer 3

In addition to the check before downloading you can do try-catch. This download is likely to throw an error if file is missing or something (load does, but I don't have download). You get this error for load:
Error using load
Unable to read file 'lala.m'. No such file or directory.
Now the same with try-catch:
try
load('lala.m')
catch
disp('No such file')
end
It will display No such file, which might not be the real error thrown by load, but you can do multiple catches.
This doesn't have a large advantage when the only thing that can go wrong is "file does not exist", but if you have multiple possible fail points you can have single try-catch (if you don't care what went wrong, just that something did) instead of a long cascade of ifs checking everything.