Is there a way to assign the 'end' value to a variable?

Hello everyone,

this is my first question. Sorry if it's too simple or easy, but i couldn't find the answer at Google.

I was programming a simple script to locate all file names in a folder. Most of them had a similar name, with '_' character in it (ex: file_name.mat), but not all of them. I wanted only the firt part of the name, from those with '_' character.

I did something like this (is a shorter version of my code):

 for i=1:length(list_of_files)
    b=findstr('_',list_of_files(i).name)-1;

    if isempty(b)
        b='end' %That's my question
    end

    another_list{i}=list_of_files(i).name(1:b)
 end

I know that i could just use 'length(list_of_files(i).name)' instead of 'end', but i was out of curiosity to ask about if it was possible to assign 'end' to a variable, and how?

I've already tried something like:

 b=end;
 b='end';

Doesn't work!

Thanks

Sergi

Answer 1

[Steve Eddins]

No, you can't assign the indexing value of "end" to a variable. You have to use size, or length, or numel in order to assign the value to a variable.

[Jan]

It is surprising that 'end' does not work, while ':' is accepted as string. Anyhow, size() is better. +1

So Sergej needs: b = length(list_of_files(i).name).

Answer 2

[F.]

And did you try strread ??

    [A, B, ...] = strread('str', 'format')

[ NameStart, NameEnd ] = strread( list_of_files(i).name, '%s_%s')

Answer 3

[Sergi]

Thanks F.

The thing is i've already solved my problem getting parts from a string.

Thanks anyway for the strread() tip, but i'm still out of curiosity if it is possible to assign 'end' to a variable.

I'm sure all the examples using 'end' I can think of can be equaly programmed with other options, but maybe one day it'll be need it, so

is there a way to use 'end value' from a variable?

Cheers

Sergi

[Jan]

Please, Sergej, do not post important information to define the problem as answer. Editing the original question is much more efficient for adding clarifications.

Please note that the method you use for copying strings is not efficient. A=B(1:end) takes remarkably more time then A=B, while the later creates even a shared data copy and saves memory in addition. Therefore the answers do not hit the point of your question. We hesitate to fix an inefficient method, when the problem does not occur in efficient solutions.

[Sergi]

Thanks to all. Sorry about the posting stuff. My first time!! My bad.

[Sergi]

I'm aware of a=b being better than a=b(1:end). Sorry, it was just a not very good example the one i wrote. My real routine is needed to extract just a part from the whole string, never all of it...

thanks anyway

Answer 4

[Jan]

for i=1:length(list_of_files)
  b = strfind(list_of_files(i).name, '_') - 1;  % FINDSTR is deprecated
  if isempty(b)
    another_list{i} = list_of_files{i};  % Curly braces!
  else.name(1:b)
    another_list{i} = list_of_files{i}(1:b(1));
  end
end

"b(1)" considers even multiple underscores. But if an underscore appears, the file extension is cut off also, while it is kept for names without underscores.

strtok can do the conversion also. You can even avoid the loop:

another_list = strtok(list_of_files, '_');

But the file extension problem is still not addressed.

[Sergi]

Thanks to all

Answer 5

[Daniel Shub]

While I have not verified it, I think if you really wanted to assign

b='end'

and then use it for indexing, that you could overload subsref. I cannot think of a good reason you would want to do this.