# Using strcmp on multiple strings to get a logical array

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Marc Cousoulis on 12 Jan 2017
Edited: James Tursa on 16 Jan 2017
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 on 15 Jan 2017
Note:
Event = ['a1','b1','a1','c1','b1']';
is the same as:
Event = ('a1b1a1c1b1').';
Most likely you mean a cell string instead.

Kirby Fears on 12 Jan 2017
Edited: Kirby Fears on 12 Jan 2017
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)
##### 2 CommentsShowHide 1 older comment
Jan on 15 Jan 2017
strcmp does not accept: strcmp(Event, Check.') and this does not work also:
bsxfun(@strcmp, Event, Check.') % ERROR!
What a pity.

Guillaume on 13 Jan 2017
Edited: Guillaume on 13 Jan 2017
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

John BG on 13 Jan 2017
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
thanks in advance for time and attention
John BG
Jan on 15 Jan 2017
@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.