# Find matches without repetition from two cell arrays + extra condition

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Alberto Cuadra Lara on 6 Dec 2018
Hello,
In order to reduce the size of a matrix I need to find all the elements of the periodic table (patterns - cell 1) of all the species considered (cell 2). Also, it has to take in account every number as the end of the evaluable pattern.
Example:
Elements = {'H', 'He', 'Li', .... };
NameSpecies = {'H2','O2','H2O2','CH2OH','C'};
Desired_Result = {'H','O','C'};
At the moment I'm using this piece of code that I found on the net
Match=cellfun(@(x) ismember(x,NameSpecies), Elements, 'UniformOutput', 0);
Elements = Elements(cell2mat(Match));
but this function is only going to give me the same individuals elements, in the case of the example the result is
Result = {'C'};
Any suggestion to tackle it without brute force?
##### 2 CommentsShowHide 1 older comment
Alberto Cuadra Lara on 6 Dec 2018
Bruno has already resolved the question. Okay pattern maybe was not the best description of the problem. The problem consisted to find the common elements of the set of species considered.
Thanks.

Bruno Luong on 6 Dec 2018
You don't even need the period table, assuming element start with an Uppercase eventually followed by lower-case
NameSpecies = {'He','O2','H2O2','CH2OH','C'};
Tmp = cell(size(NameSpecies));
for k = 1:length(Tmp)
Specie = NameSpecies{k};
Specie(Specie>='0' & Specie<='9') = ' ';
idx = find([(Specie>='A' & Specie<='Z'), true]);
lgt = diff(idx);
Tmp{k} = strtrim(mat2cell(Specie, 1, lgt));
end
El = unique(cat(2,Tmp{:}))
The result is:
El =
1×4 cell array
{'C'} {'H'} {'He'} {'O'}
Alberto Cuadra Lara on 6 Dec 2018
Great!! Thank you Bruno.

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