MATLAB: Could anyone clarify the doubt with respect to the following code

idx

N_UE=10
unused_rows=1:N_UE
while ~isempty(unused_rows)
N_UE_rows=ceil(sqrt(randi(numel(unused_rows))))
rows=unused_rows(randsample(length(unused_rows),N_UE_rows))
[~,idx]=find(ismember(unused_rows,rows))
unused_rows(idx)=[]
end
If i run the code it executes My clarification is with respect to command line [~,idx]=find(ismember(unused_rows,rows)) after executing the code the result in the command window was
N_UE =
     7
unused_rows =
     1     2     3     4     5     6     7
N_UE_rows =
       2
rows =
       6     4
idx =
       4     6
unused_rows =
       1     2     3     5     7
N_UE_rows =
       2
rows =
       1     3
idx =
       1     3
unused_rows =
       2     5     7
N_UE_rows =
       2
rows =
       5     7
idx =
       2     3
unused_rows =
       2
N_UE_rows =
       1
rows =
       2
idx =
       1
unused_rows =
     Empty matrix: 1-by-0
If rows= 6  4
idx=4   6
rows = 1  3
idx=1  3
but if 
rows= 5  7
idx should be 5  7 but it shows
idx = 2  3
rows = 2
idx=1
why it is so.Could anyone clarify my doubt

Best Answer

Use the following code:
N_UE=10;
unused_rows_init=1:N_UE;
unused_rows=unused_rows_init;
while ~isempty(unused_rows)
N_UE_rows=ceil(sqrt(randi(numel(unused_rows))))
rows=unused_rows(randsample(length(unused_rows),N_UE_rows))
[~,idx]=find(ismember(unused_rows_init,rows))
unused_rows(ismember(unused_rows,rows))=[]
end
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