Hello, I have a file that has 460000 rows and 460000 columns. The upper triangle of this matrix has the actual values I'm interested in and the other cells contain "NA". My aim is to fill in the lower triangle as well. I tried reading in the file into an array of arrays and assigning  mat[j,i]=mat[i,j] where i and j are row and column indices, however I quickly ran out of memory just reading the file into a 'matrix'! I can't think of a way of assigning values to the lower triangle without reading in the entire file. Does someone know a way of achieving this? Any pointers would be appreciated. Many Thanks!

In reply to upper or lower triangular matrix to full by savita

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