strfind: how to set a cell for the pattern?

pietro (view profile)

on 11 Jul 2014
Latest activity Edited by Image Analyst

Image Analyst (view profile)

on 12 Jul 2014
Accepted Answer by Image Analyst

Image Analyst (view profile)

Hi all,

I need to set a cell as pattern for strfind without using a for. Here an example

```a={'1','2','3'};
b={'1','2'};
c=strfind(a,b)
```
```c=[1 1 [] ];
```

thanks

cheers

Sara

Sara (view profile)

on 11 Jul 2014

Elegant solutions aren't always faster; they are easier to read and save space and coding, I agree on that, but if performance is the issue, you have to test with and without the loop with the profiler (or tic toc). I was just trying to understand what the logic behind the question is.

Image Analyst

Image Analyst (view profile)

on 11 Jul 2014

```a={'1','2','3'};
b={'2','1'};
```

Do you consider that the 1 and the 2 are found/matched, or not? They are not in the same locations , but both are in both arrays.

pietro

pietro (view profile)

on 12 Jul 2014

the output should be {[1],[1],[]}.

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Image Analyst (view profile)

Answer by Image Analyst

Image Analyst (view profile)

on 12 Jul 2014
Edited by Image Analyst

Image Analyst (view profile)

on 12 Jul 2014

Here is a simple, easy to understand way that will work:

```clc; % Clear command window.
% Initialize variables.
a={'1','21','3'};
b={'2','1'};
% Initialize results.
% Let's use a simple numerical array rather than a cell array!
c = zeros(1, length(a));
% Scan each element of "a" for all the elements of "b".
for k = 1 : length(a)
for colb = 1 : length(b)
if ismember(b{colb}, a{k})
c(k) = 1;
break;
end
end
end
% Print out to command window.
c
```

Jos (10584) (view profile)

Answer by Jos (10584)

Jos (10584) (view profile)

on 11 Jul 2014
```% implicit for with CELLFUN
c = cellfun(@(x) strfind(x,b), a, 'un', 0)
```

pietro

pietro (view profile)

on 11 Jul 2014

Thanks for your reply. It doesn't work, I get the following error:

```Error using cell/strfind (line 33)
If any of the input arguments are cell arrays, the first must be a cell array of
strings and the second must be a character array.
```
```Error in @(x)strfind(x,b)
```

Titus Edelhofer (view profile)

Answer by Titus Edelhofer

Titus Edelhofer (view profile)

on 11 Jul 2014

Hi,

not exactly the same result but similar:

```ismember(a, b)
```

Titus

Chris E. (view profile)

Answer by Chris E.

Chris E. (view profile)

on 11 Jul 2014

Hello! Well I think this answers your question, it does not have a for loop, however it uses "ismember" rather then 'strfind', but I think the output is the same as what you want.

```a={'1','2','3'}
b={'1','2'}
val = ismember(a,b)
val(val == 0)=[]
c = val
```

Hope that helps!

pietro

pietro (view profile)

on 11 Jul 2014

Unfortunately I cannot use ismember because it is not really equivalent to strfind since it works only when there is an exact match. I'm sorry for not being clearly enough, but it should work also with the following case:

```a={'12','2','3'};
b={'1','2'};
```

Jos (10584) (view profile)

Answer by Jos (10584)

Jos (10584) (view profile)

on 11 Jul 2014

Then please explain the relationship between a,b,and c. Why is c{2} equal to 1?

pietro

pietro (view profile)

on 11 Jul 2014

because:

```strfind(a,b{2})
```
```[]    [1]    []
```

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