Translates matrix indices by rows into indices by columns
Translates matrix indices by rows into indices by columns.
indexByRow(dim, idxs = NULL, ...)
The current implementation does not support long-vector indices,
because both input and output indices are of type integers.
This means that the indices in argument idxs can only be in
range [1,2^31-1]. Using a greater value will be coerced to
NA_integer_. Moreover, returned indices can only be in the
same range [1,2^31-1].
Henrik Bengtsson
dim <- c(5, 4) X <- matrix(NA_integer_, nrow = dim[1], ncol = dim[2]) Y <- t(X) idxs <- seq_along(X) # Assign by columns X[idxs] <- idxs print(X) # Assign by rows Y[indexByRow(dim(Y), idxs)] <- idxs print(Y) stopifnot(X == t(Y))
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