What to do about zeros in filenames when importing data to cell using sprintf ...

This seems like it would be a fairly common problem, yet I haven't found any documentation or on Answers relating to this. So if anyone has a handy link, that'd be great (maybe it's too specific).

I have ten datasets in *.MAT format named sequentially:

Position01.mat, Position02.mat ... through to ... Position10.mat

Importing Position01 to Position09 to a cell is no issue, but opening and importing "Position10.mat" is made tricky because the number in its filename is "formatted" differently; specifically, doesn't start with zero. So, I'm wondering if I can keep my filenames, which keep the files nicely organised and in order outside MATLAB and find a workaround for dealing with "Position10.mat".

I'm currently using these lines to import the files ...

NumFiles    = 10;
AudioCell   = cell(1, NumFiles);

for k = 1: NumFiles
  Position      = sprintf('Position0%d.mat', k);
  AudioCell{k}  = importdata(Position);
end

It imports Position01 - Position09 exactly how I want, but Position10 has me stumped. Is changing the *.MAT filenames to "Position1", "Position2" and so on, my only decent option? So ...

Position      = sprintf('Position%d.mat', k);

Thanks in advance!

Answer 1

[Ameer Hamza]

No, this is not the only option. The correct way is to use format specifier of sprintf() to add zeros automatically

sprintf('Position%02d.mat', k);

This will try to replace %02d with 2 digits. If k = 1 to 9, then it will append a zero.

[Peter Beringer]

Ah, excellent! So, "&02d" denotes two digits?

[Peter Beringer]

What is that method/symbol called (the "%02d" part)? Hopefully I can find documentation that has all those kind of codes used for indicating where and what type of characters the code should look for (I hope that makes sense). Thanks!

[Ameer Hamza]

I am glad to be of help!

This part is called formatSpec. Read all about it here: https://www.mathworks.com/help/matlab/ref/sprintf.html#btf_bfy-1_sep_shared-formatSpec

[Peter Beringer]

I really appreciate it. Thanks so much again!

And thanks a bunch for the link! I reckon sometimes just finding out the correct terminology for something - "formatSpec", for example, which is a term I hadn't even come across when trying to solve this - makes such a huge difference when looking things up; vague search terms make wading through the results a frustrating task. Maybe sometimes the best questions to ask are just things like "what's this oscure looking character sequence called?". Hehe.

Cheers!

[Ameer Hamza]

Ture, sometimes all one needs is a correct hint, and the rest is easy to figure out.