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Hi, I have a huge matrix (4000 * 2000 data points) and I would like to retrieve the coordinates (column and row) for the top 50 (or x) values. Some positions in the matrix have NA as a value. These should be discarded. My current method is to replace all NAs by 0, then rank all the values and then extract the positions with the 50 highest ranks. It is very time-consuming! Is there a simpler