MATLAB Central Newsreader - find an element in a cell data type

find an element in a cell data type

karlo gonzales — Mon, 14 May 2012 16:43:07 +0000

Hi ,

suppose you have a cell variable type as : LABEL= {'AB', 'CD', 'EF',.....'YZ' } ;

and you want to check if another variable( e.g., var1='CD') is one of those in LABEL,

using LABEL==var1 or find(LABEL,var1) both gives error.

what's the correct way to check if the "var1" is one element of the LABEL?

thanks

Re: find an element in a cell data type

Bruno Luong — Mon, 14 May 2012 16:57:12 +0000

"karlo gonzales" wrote in message <jorcmr$skc$1@newscl01ah.mathworks.com>...
> Hi ,
>
> suppose you have a cell variable type as : LABEL= {'AB', 'CD', 'EF',.....'YZ' } ;
>
> and you want to check if another variable( e.g., var1='CD') is one of those in LABEL,
>
> using LABEL==var1 or find(LABEL,var1) both gives error.
>
> what's the correct way to check if the "var1" is one element of the LABEL?

any(strcmp('CD', LABEL)) % return the true if var1 is found
find(strcmp('CD', LABEL)) % return where is 'CD' in LABEL

% Bruno

Re: find an element in a cell data type

karlo gonzales — Mon, 14 May 2012 17:19:07 +0000

"Bruno Luong" <b.luong@fogale.findmycountry> wrote in message <jordh8$2v3$1@newscl01ah.mathworks.com>...
> "karlo gonzales" wrote in message <jorcmr$skc$1@newscl01ah.mathworks.com>...
> > Hi ,
> >
> > suppose you have a cell variable type as : LABEL= {'AB', 'CD', 'EF',.....'YZ' } ;
> >
> > and you want to check if another variable( e.g., var1='CD') is one of those in LABEL,
> >
> > using LABEL==var1 or find(LABEL,var1) both gives error.
> >
> > what's the correct way to check if the "var1" is one element of the LABEL?
>
> any(strcmp('CD', LABEL)) % return the true if var1 is found
> find(strcmp('CD', LABEL)) % return where is 'CD' in LABEL
>
> % Bruno

Exactly what i was looking for. Than you so much Bruno!.

Re: find an element in a cell data type

Ben — Mon, 14 May 2012 20:53:07 +0000

> >
> > any(strcmp('CD', LABEL)) % return the true if var1 is found
> > find(strcmp('CD', LABEL)) % return where is 'CD' in LABEL

I would've suggested ismember, but you're right -- any(strcmp()) works as well. In fact, it seems much faster. Why is ismember slower?

Re: find an element in a cell data type

Bruno Luong — Mon, 14 May 2012 21:03:07 +0000

"Ben" wrote in message <jorrbj$7lg$1@newscl01ah.mathworks.com>...

>
> I would've suggested ismember, but you're right -- any(strcmp()) works as well. In fact, it seems much faster. Why is ismember slower?

Just a guess, but there are perhaps one or two reasons:

1) ismember() works on two cell arrays, the internal engine must do a sorting of the strings, thus slow. strcmp() simply goes through the cell and compares two strings. On the complexity, algorithm used by strcmp is better when one array is a single strings.

2) ismember might have more overhead.

Bruno