understanding matlab snippet of code - matlab

Question

I'm getting stuck in what's happening here. This is my understanding, so, C{1} has a column of strings. something like this:
A231
A354
A356
A234
.
.
pattern continues until the end
ids then gets a copy of that column, and idmlh becomes the second element of the cell array which is a matrix in this case. Then an empty array is created in idsCo and idx. Then it goes through all the rows in the column of ids and checks if what is in that row is found in another data structure which has similar dimensions to ids, parIDs. So this is where the first confusion comes in,
if it isnt a member then it stores the index value in idx ? And if it is a member then what happens exactly?
Im most uncertain about this part:
else
[~,~,ii] = intersect(ids{cnt}, parIDs) ;
idsCo = [idsCo ; Lbll(ii) ] ;
end
end
ids(idx) = [] ;
idmlh(idx,:) = [] ;
Below is the full code:
ids = C{1} ;
idmlh = C{2} ;
idsCo = [] ;
idx = [] ; label for
for cnt=1:length(ids)
if ~ismember(strtrim(ids{cnt}), parIDs)
idx = [idx cnt] ;
else
[~,~,ii] = intersect(ids{cnt}, parIDs) ;
idsCo = [idsCo ; Lbl(ii) ] ;
end
end
ids(idx) = [] ;
idmlh(idx,:) = [] ;

Answer 1

1: ids = C{1} ;
2: idmlh = C{2} ;
3: idsCo = [] ;
4: idx = [] ; label for
5: for cnt=1:length(ids)
6: if ~ismember(strtrim(ids{cnt}), parIDs)
7: idx = [idx cnt] ;
8: else
9: [~,~,ii] = intersect(ids{cnt}, parIDs) ;
10: idsCo = [idsCo ; Lbl(ii) ] ;
11: end
12: end
13: ids(idx) = [] ;
14: idmlh(idx,:) = [] ;
It is essential to know what strtrim and intersect do...
In the loop over all elements of ids it checks whether the cnsth element is part of parIDs array.
If it is not (~ismember is evaluated as true) then actual cnt value is appended to idx array.
If it is member (~ismember is evaluated as false) then it asks what elements of ids{cnt} (1x1) and parIDs (Nx1) are in both arrays. Values of the element is ignored ([~,...), index of this element in first array is also ignored (...,~,...). Index of the element in second array is assigned to ii (...,ii]=).
Then the iith element of Lbl is appended to idsCo array.
In the end the elements of ids and their counterparts in idmlh that aren't in parIDs are replaced by empty array.