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I need to get the row and column name of the smallest element of a matrix
> mat = matrix(data=runif(12), nrow = 4, ncol=4) > rownames(mat) = colnames(mat) = letters[1:4] > > mat a b c d a 0.3167865 0.6958895 0.4233572 0.3167865 b 0.1042599 0.1552235 0.8461520 0.1552235 c 0.6286461 0.9749868 0.2390978 0.6286461 d 0.5923721 0.7823673 0.8427426 0.5923721 > min = min(mat) > min > 0.1042599 In this example I'd like to get "a" and "b"
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M = min( A ,[], dim ) returns the minimum element along dimension dim . For example, if A is a matrix, then min(A,[],2) is a column vector containing the minimum value of each row.
We have made use of the max() function which is used to find the maximum element present in an object. This object can be a Vector, a list, a matrix, a data frame, etc. The “which()” function is used to get the index or position of the value which satisfies the given condition.
Naming Rows and Columns of a Matrix in R Programming – rownames() and colnames() Function. rownames() function in R Language is used to set the names to rows of a matrix.
Pair Comparison (Efficient method): Select two elements from the matrix one from the start of a row of the matrix another from the end of the same row of the matrix, compare them and next compare smaller of them to the minimum of the matrix and larger of them to the maximum of the matrix.
> inds = which(mat == min(mat), arr.ind=TRUE) > inds row col a 1 2 > rnames = rownames(mat)[inds[,1]] > cnames = colnames(mat)[inds[,2]] This will give you the row/column names for each entry that equals the minimum value; if you just want the first one, you could only check inds[1,1] and inds[1,2].
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