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# file nnet/multiedit.q copyright (C) 1994-9 W. N. Venables and B. D. Ripley
#
multiedit <- function(x, class, k=1, V=3, I=5, trace=TRUE)
{
n1 <- length(class)
class <- unclass(class)
index <- 1:n1
pass <- lpass <- 0
repeat{
if(n1 < 5*V) {
warning("retained set is now too small to proceed")
break
}
pass <- pass + 1
sub <- sample(V, length(class), replace=TRUE)
keep <- logical(length(class))
for (i in 1:V){
train <- sub==i
test <- sub==(1 + i%%V)
keep[test] <- (knn(x[train, , drop=FALSE], x[test, , drop=FALSE],
class[train],k) == class[test])
}
x <- x[keep, , drop=FALSE]; class <- class[keep]; index <- index[keep]
n2 <- length(class)
if(n2 < n1) lpass <- pass
if(lpass <= pass - I) break
n1 <- n2
if(trace) cat(paste("pass ", pass," size ", n2, "\n"))
}
index
}
condense <- function(train, class, store=sample(seq(n), 1), trace=TRUE)
{
n <- length(class)
bag <- rep(TRUE, n)
bag[store] <- FALSE
repeat {
if(trace) print(seq(n)[!bag])
if(sum(bag) == 0) break
res <- knn1(train[!bag,,drop = FALSE], train[bag,,drop = FALSE], class[!bag])
add <- res != class[bag]
if(sum(add) == 0) break
cand <- (seq(n)[bag])[add]
if(length(cand) > 1) cand <- sample(cand, 1)
bag[cand] <- FALSE
}
seq(n)[!bag]
}
reduce.nn <- function(train, ind, class)
{
n <- length(class)
rest <- seq(n)[-ind]
# this must be done iteratively, not simultaneously
for(i in sample(ind)) {
res <- knn1(train[-c(rest,i),,drop=FALSE], train[c(rest,i),,drop=FALSE],
class[-c(rest,i)])
if(all(res == class[c(rest,i)])) rest <- c(rest,i)
}
seq(n)[-rest]
}
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