Using strcmp on multiple strings to get a logical array

I want to check for the occurrence of 3 possible events in a series of events..

Event = ['a1','b1','a1','c1','b1']';

Check = {'a1','b1','c1'}';

LogA(:,1) = strcmp(Event,Check{1});

LogA(:,2) = strcmp(Event,Check{2});

LogA(:,3) = strcmp(Event,Check{3});

This gives me a 5x3 logical array, but is there a way to do it without calling each column individually? i.e., what if I had 100 strings I wanted to check for and the goal was to have a 5x100 logical array? I don't want to use a "for-loop". I'm assuming there is some matrix way to do this.

[Jan]

Note:

Event = ['a1','b1','a1','c1','b1']';

is the same as:

Event = ('a1b1a1c1b1').';

Most likely you mean a cell string instead.

Answer 1

[Kirby Fears]

There's really nothing wrong with a for loop in this case. However, cellfun is probably what you're looking for:

 Event = {'a1','b1','a1','c1','b1'}'; 
 Check = {'a1','b1','c1'}';  
 l = cellfun(@(c)strcmp(c,Event),Check,'UniformOutput',false);

This produces a cell array the size of Check with logical arrays the size of Event.

You can index like this:

 l{index1}(index2)

[Stephen23]

Also simple to convert to a logical array:

>> Event = {'a1','b1','a1','c1','b1'};
>> Check = {'a1','b1','c1'};
>> X = cellfun(@(c)strcmp(c,Event),Check,'UniformOutput',false);
>> vertcat(X{:})
ans =
   1   0   1   0   0
   0   1   0   0   1
   0   0   0   1   0

[Jan]

strcmp does not accept: strcmp(Event, Check.') and this does not work also:

bsxfun(@strcmp, Event, Check.')   % ERROR!

What a pity.

Answer 2

[Guillaume]

Another option which may or may not be faster than cellfun(...):

Event = {'a1','b1','a1','c1','b1'}'; 
Check = {'a1','b1','c1'}';  
LogA = false(numel(Event), numel(Check));
[~, loc] = ismember(Event, Check);
LogA(sub2ind(size(LogA), 1:numel(Event), loc.')) = true

Answer 3

[John BG]

Marc

1.

If all 2nd halves of the strings contained in Event is '1', it is reasonable to ignore the entire column:

Event = ['a1';'b1';'a1';'c1';'b1'];
Event_num=double(Event)
 =
    97    49
    98    49
    97    49
    99    49
    98    49

E=Event_num(:,1)';
E =
  97    98    97    99    98

2.

Same applies to Checks

Check = ['a1';'b1';'c1']; 
Check_num=double(Check)
=
    97    49
    98    49
    99    49

C=Check_num(:,1)';
C =
  97    98    99

3.

Occurence of events are listed in variable occ

[Lie,occ]=ismember(E,C)
Lie =
     1     1     1     1     1
occ =
     1     2     1     3     2

4.

check

Check(occ)
=
abacb

meaning occ contains the occurrences: a1 b1 a1 c1 b1

if you find these lines useful would you please mark my answer as Accepted Answer?

To any other reader, if you find this answer of any help please click on the thumbs-up vote link,

thanks in advance for time and attention

John BG

<mailto:[e-mail] [e-mail]>

[Jan]

There is no advantage in converting the strings to doubles, because ismember works on CHAR-arrays directly.

[John BG]

Well, it's Marc's question, why don't you let Marc decide?

[John BG]

To Marc Cousloulis:

did you mark this question as Accepted Answer or did some one else mark it as if you had accepted it?

[Guillaume]

As is clearly explained in the help page, answers can only be accepted by somebody else after 7 days of inactivity by the original author.

[Jan]

@John BG: Marc can still decide, even if he knows why your solution in not efficient. Other readers and you can profit from this information also.