Why does contains(var1, var2) find matches in two different string arrays?

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Hamza Imtiaz
Hamza Imtiaz 2021-3-6
编辑： Hamza Imtiaz 2021-3-7
I have two string arrays, var1 and var2. When I use the contains function, I get a match, despite these two strings having zero common values.
String 1:
ch_names = {'FP1','FPz','FP2','AF7','AF3','AF4','AF8','F7','F5','F3',...
'F1','Fz','F2','F4','F6','F8','FT7','FC5','FC1','FC2','FC6','FT8',...
'T7','C5','C3','C1','Cz','C2','C4','C6','TP7','CP3','CP1','CP2',...
'CP4','TP8','P7','P5','P3','P1','Pz','P2','P4','P6','P8','PO7',...
'PO3','PO4','PO8','O1','Oz','O2','Iz'};
String 2:
MEG_ch = {'EOG061','EOG062','ECG063','STI101','STI201','STI301',...
'MISC201','MISC202','MISC203','MISC204','MISC205','MISC206','MISC301',...
'MISC302','MISC303','MISC304','MISC305','MISC306'};
Code used to compare the variables:
contains(string(MEG_ch), string(ch_names))
% Output:
%
% ans =
% 1×18 logical array
% 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1
The purpose of this code is to see if any string in ch_names (var2) occurs in MEG_ch (var1). If it does occur, then var1 gets categorized a certain way.
Also, if i switch var2 and var1's position in the contains function, I get the expected behavior of no matches. i.e contains(string(ch_names), string(MEG_ch)).
If there are more efficient ways to do this or I can explain a certain point in more detail, I welcome your suggestions.

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采纳的回答

madhan ravi
madhan ravi 2021-3-6
Ran in:
ch_names = {'FP1','FPz','FP2','AF7','AF3','AF4','AF8','F7','F5','F3',...
'F1','Fz','F2','F4','F6','F8','FT7','FC5','FC1','FC2','FC6','FT8',...
'T7','C5','C3','C1','Cz','C2','C4','C6','TP7','CP3','CP1','CP2',...
'CP4','TP8','P7','P5','P3','P1','Pz','P2','P4','P6','P8','PO7',...
'PO3','PO4','PO8','O1','Oz','O2','Iz'};
MEG_ch = {'EOG061','EOG062','ECG063','STI101','STI201','STI301',...
'MISC201','MISC202','MISC203','MISC204','MISC205','MISC206','MISC301',...
'MISC302','MISC303','MISC304','MISC305','MISC306'};
any(ismember(ch_names, MEG_ch)) % any matches at all 0 means false and vice versa
ans = logical
0
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Walter Roberson
Walter Roberson 2021-3-6
'MISC202' (8th element)
'C2' (28th element of pattern)
'MISC202' contains 'C2' so so that is a match.
The contains() operator does not compare for entire strings: it compares for substrings.

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