to use ismember with arraycell

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Luca Re
Luca Re on 13 Oct 2024
Edited: Luca Re on 14 Oct 2024
gg =
4×1 cell array
{'A' }
{'A'}
{'B' }
{'A' }
[a,b]=ismember({'A'},gg)
a =
logical
1
b =
1
is not corret..i expect 1 1 0 1
  1 Comment
Stephen23
Stephen23 on 13 Oct 2024
"is not corret.."
It is correct: the first input 'A' is definitely a member of the second input:
ismember('A',{'A','A','B','A'})
ans = logical
1
"i expect 1 1 0 1"
ismember({'A','A','B','A'},'A')
ans = 1x4 logical array
1 1 0 1

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Accepted Answer

Sameer
Sameer on 13 Oct 2024
Edited: Sameer on 13 Oct 2024
Hi Luca
The "ismember" function is designed to work with arrays, and when using it with cell arrays of strings, it checks for membership of each element in the cell array. However, it returns a single logical value for the entire array when you provide a single element to check against the cell array.
To achieve the result you expect , you can use "strcmp" to compare each element in the cell array individually.
Here's how you can do it:
gg = {'A'; 'A'; 'B'; 'A'};
a = strcmp('A', gg);
disp(a);
1 1 0 1
Please refer to the below MathWorks documentation link:
Hope this helps!
  1 Comment
Walter Roberson
Walter Roberson on 13 Oct 2024
[a,b]=ismember({'A'},gg)
answers the question of whether 'A' occurs in gg, as a yes or no answer in a and the index inside gg it occurs in b . {'A'} is a single element so you get a single answer.
[a,b]=ismember(gg, {'A'})
on the other hand iterates through the elements of gg, and for each one answers the question of whether the element occurs within {'A'} . gg is length 4 so the answer in a will be of length 4 -- [gg{1} is in {'A'}, gg{2} is in {'A'}, gg{3} is in {'A'}, gg{4} is in {'A'}] .

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More Answers (2)

Pavl M.
Pavl M. on 13 Oct 2024
gg = {'A' ,'A','B' ,'A' }
gg = 1x4 cell array
{'A'} {'A'} {'B'} {'A'}
a = cell2mat(gg)
a = 'AABA'
g = zeros(1,length(a));
g(find(a=='A')) = 1
g = 1×4
1 1 0 1
<mw-icon class=""></mw-icon>
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  7 Comments
Pavl M.
Pavl M. on 14 Oct 2024
Edited: Pavl M. on 14 Oct 2024
clc
clear all
close all
%% Inputs ( from a methode ):
ex = 'STA';
dd = { 'STA', 'STAT', 'STA', 'STATT' } ;
%% Detection module:
% contains(dd, 'STA') is not yet implemented as built-in in TCE Octave
if length(ex)>1
strcmp(dd,ex)
else
a = cell2mat(dd);
g = zeros(1,length(a));
g(find(a==ex)) = 1
end
ans = 1x4 logical array
1 0 1 0
Luca Re
Luca Re on 14 Oct 2024
Edited: Luca Re on 14 Oct 2024
ok but i think this solution is better: (solution of Sameer)
gg = {'AB'; 'AA'; 'BB'; 'AC'};
a = strcmp('AC', gg)
It has fewer lines of code..it seems faster to me

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Steven Lord
Steven Lord on 13 Oct 2024
Both outputs are the same size as the first input.
gg = {'A'; 'A'; 'B'; 'A'};
[a1,b1]=ismember({'A'},gg)
a1 = logical
1
b1 = 1
[a2, b2] = ismember(gg, {'A'})
a2 = 4x1 logical array
1 1 0 1
b2 = 4×1
1 1 0 1
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  2 Comments
Steven Lord
Steven Lord on 14 Oct 2024
Based on a revised example you posted as a comment on another answer, it looks like you're not trying to find cells in a cell array that are an exact match for a specific character. It looks like you're trying to find cells that contain that character anywhere inside the word they contain. If that is correct:
gg = { 'STA' , 'STAT' , 'STA' , 'STATT' }
gg = 1x4 cell array
{'STA'} {'STAT'} {'STA'} {'STATT'}
contains(gg, 'A')
ans = 1x4 logical array
1 1 1 1
gg{3} = 'STEM' % Replace one of the words with one not containing 'A'
gg = 1x4 cell array
{'STA'} {'STAT'} {'STEM'} {'STATT'}
contains(gg, 'A')
ans = 1x4 logical array
1 1 0 1
Or you could use other string related functions instead of contains. Some examples include startsWith and endsWith.

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