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

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.

Answer 1

[madhan ravi]

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

[Hamza Imtiaz]

Thank you for your solution.

However, I'm looking for why there was a match when contains was used. As far as I understand, there are no patterns that should have been found in the first string array, unless I'm missing something.

[Walter Roberson]

'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.

[Hamza Imtiaz]

Walter,

Thank you, that makes sense.