R FAQ
How does R handle missing values?

http://www.ats.ucla.edu/stat/r/faq/missing.htm


I hope this may useful for you.

我觉得可以有以下几种方法：
1、直接删除
2、均值替代
3、最邻近方法补充，代码如下：
library(cluster)
tData2<-tData[1:500,]
dist.mtx <- as.matrix(daisy(tData2,stand=T))

central.value <- function(x) {
if (is.numeric(x)) median(x,na.rm=T)
else if (is.factor(x)) levels(x)[which.max(table(x))]
else {
f <- as.factor(x)
levels(f)[which.max(table(f))]
}
}


for(r in which(!complete.cases(tData2)))
{
   tData2[r,which(is.na(tData2[r,]))] <-
   apply(data.frame(tData2[c(as.integer(names(sort(dist.mtx[r,])[2:11]))),
   which(is.na(tData2[r,]))]), 2,central.value)
}

受教了~~~~