Created
January 30, 2016 05:17
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knnImputation
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function (data, k = 10, scale = T, meth = "weighAvg", distData = NULL) | |
{ | |
n <- nrow(data) | |
if (!is.null(distData)) { | |
distInit <- n + 1 | |
data <- rbind(data, distData) | |
} | |
else distInit <- 1 | |
N <- nrow(data) | |
ncol <- ncol(data) | |
nomAttrs <- rep(F, ncol) | |
for (i in seq(ncol)) nomAttrs[i] <- is.factor(data[, i]) | |
nomAttrs <- which(nomAttrs) | |
hasNom <- length(nomAttrs) | |
contAttrs <- setdiff(seq(ncol), nomAttrs) | |
dm <- data | |
if (scale) | |
dm[, contAttrs] <- scale(dm[, contAttrs]) | |
if (hasNom) | |
for (i in nomAttrs) dm[, i] <- as.integer(dm[, i]) | |
dm <- as.matrix(dm) | |
nas <- which(!complete.cases(dm)) | |
if (!is.null(distData)) | |
tgt.nas <- nas[nas <= n] | |
else tgt.nas <- nas | |
if (length(tgt.nas) == 0) | |
warning("No case has missing values. Stopping as there is nothing to do.") | |
xcomplete <- dm[setdiff(distInit:N, nas), ] | |
if (nrow(xcomplete) < k) | |
stop("Not sufficient complete cases for computing neighbors.") | |
for (i in tgt.nas) { | |
tgtAs <- which(is.na(dm[i, ])) | |
dist <- scale(xcomplete, dm[i, ], FALSE) | |
xnom <- setdiff(nomAttrs, tgtAs) | |
if (length(xnom)) | |
dist[, xnom] <- ifelse(dist[, xnom] > 0, 1, dist[, | |
xnom]) | |
dist <- dist[, -tgtAs] | |
dist <- sqrt(drop(dist^2 %*% rep(1, ncol(dist)))) | |
ks <- order(dist)[seq(k)] | |
for (j in tgtAs) if (meth == "median") | |
data[i, j] <- centralValue(data[setdiff(distInit:N, | |
nas), j][ks]) | |
else data[i, j] <- centralValue(data[setdiff(distInit:N, | |
nas), j][ks], exp(-dist[ks])) | |
} | |
data[1:n, ] | |
} | |
<environment: namespace:DMwR> |
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