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From: Ralph Mettier on 2 Aug 2010 04:30
I recently ran into a question from a new Matlab user, that totally stumped me. Not only couldn't I fin the answer in the help files, I frankly can't even think of a way to formulate the question for a search. So I turn to you guys:

We all use functions that return 1D arrays (row or column vector, doesn't matter), for instance

commas=findstr('one, two, three',',');

Now in this example, if I want the first occurance, I'll usually add another line like:

firstcomma=commas(1);

and this works fine. But is it possible to do that in one? Is there something like

firstelement(vector) which would return the first element of whatever the inner function returns?
I realize that something like this would be exceedingly simple to write, but 1) why re-invent the wheel, especially when the original wheelmaker make much better wheel than I do, an 2) 'write it yourself' isn't a particularly helpful answer for a new user.

So? Any ideas?
From: Joshua Arnott on 2 Aug 2010 05:20
"Ralph Mettier" <itsmyspam(a)gmail.com> wrote in message <i35vmt$c8r$1(a)fred.mathworks.com>...
> I recently ran into a question from a new Matlab user, that totally stumped me. Not only couldn't I fin the answer in the help files, I frankly can't even think of a way to formulate the question for a search. So I turn to you guys:
>
> We all use functions that return 1D arrays (row or column vector, doesn't matter), for instance
>
> commas=findstr('one, two, three',',');
>
> Now in this example, if I want the first occurance, I'll usually add another line like:
>
> firstcomma=commas(1);
>
> and this works fine. But is it possible to do that in one? Is there something like
>
> firstelement(vector) which would return the first element of whatever the inner function returns?
> I realize that something like this would be exceedingly simple to write, but 1) why re-invent the wheel, especially when the original wheelmaker make much better wheel than I do, an 2) 'write it yourself' isn't a particularly helpful answer for a new user.
>
> So? Any ideas?

What you're describing is called cascading indexing. It's supported in some languages (e.g., Perl) but not in Matlab. Have a search for previous threads to get the full argument, but basically it's leads to less-legible code, and common syntax implementations clash with existing Matlab syntax.

Josh.
From: Walter Roberson on 2 Aug 2010 11:47
Ralph Mettier wrote:

> We all use functions that return 1D arrays (row or column vector,
> doesn't matter), for instance
> commas=findstr('one, two, three',',');
>
> Now in this example, if I want the first occurance, I'll usually add
> another line like:
>
> firstcomma=commas(1);
>
> and this works fine. But is it possible to do that in one? Is there
> something like
>
> firstelement(vector) which would return the first element of whatever
> the inner function returns?
> I realize that something like this would be exceedingly simple to write,
> but 1) why re-invent the wheel, especially when the original wheelmaker
> make much better wheel than I do, an 2) 'write it yourself' isn't a
> particularly helpful answer for a new user.

The built-in function for this is subsref()

subsref(findstr('one, two, three',','), struct('type','[]', 'subs', {{1}}))

This is a case where it is much easier to write your own function:

firstelement = @(v) v(1);

firstelement( findstr('one, two, three',',') )
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