37 lines
853 B
R
37 lines
853 B
R
ind2subv <- function(siz, ndx) {
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# IND2SUBV Like the built - in ind2sub, but returns the answer as a row vector.
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# sub <- ind2subv(siz, ndx)
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# siz and ndx can be row or column vectors.
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# sub will be of size length(ndx) * length(siz).
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# Example
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# ind2subv([2 2 2], 1:8) returns
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# [1 1 1
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# 2 1 1
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# ...
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# 2 2 2]
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# That is, the leftmost digit toggle fastest.
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#
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# See also SUBV2IND
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n <- length(siz)
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if (n == 0) {
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sub <- ndx
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return(sub)
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}
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if (all(siz == 2)) {
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sub <- t(vapply(ndx, function(x) dec2bitv(x - 1, n), c(0, 0, 0)))
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sub <- sub[, seq(n, 1, - 1)] + 1
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return(sub)
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}
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cp <- c(1, cumprod(t(siz[])))
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ndx <- ndx[] - 1
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sub <- zeros(length(ndx), n)
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for (i in seq(n, 1, -1)) {# i'th digit
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sub[, i] <- floor(ndx / cp[i]) + 1
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ndx <- ndx %% cp[i]
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}
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return(sub)
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}
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