There's not enough detail in your question. Let's assume you have a vector of data "x" and a vector of QC values "qc". I assume the qc values are numeric or logical.
If they are logical and 'true' means "keep",
x(qc) %this eliminates any of the bad data
% or
x(qc) = NaN; % This replaces any of the bad data with "missing" data
The benefit of the 2nd line above is that the size and index values of 'x' do not change.
If your qc values are numeric and range from j to i, you can set a threshold 't' where any qc values greater than t are accepted.
xAccepted = x(qc > t);
% or
x(qc <= t) = NaN;
