我试图通过将“knnImpute”传递给Caret的train()方法的preProcess参数来估算值。根据以下示例,似乎不会估算值,保留为NA,然后忽略。我做错了什么?
非常感谢任何帮助。
library("caret")
set.seed(1234)
data(iris)
# mark 8 of the cells as NA, so they can be imputed
row <- sample (1:nrow (iris), 8)
iris [row, 1] <- NA
# split test vs training
train.index <- createDataPartition (y = iris[,5], p = 0.80, list = F)
train <- iris [ train.index, ]
test <- iris [-train.index, ]
# train the model after imputing the missing data
fit <- train (Species ~ .,
train,
preProcess = c("knnImpute"),
na.action = na.pass,
method = "rpart" )
test$species.hat <- predict (fit, test)
# there is 1 obs. (of 30) in the test set equal to NA
# this 1 obs. was not returned from predict
Error in `$<-.data.frame`(`*tmp*`, "species.hat", value = c(1L, 1L, 1L, :
replacement has 29 rows, data has 30
UPDATE :我已经能够直接使用preProcess函数来估算值。我仍然不明白为什么在列车功能中似乎没有这种情况。
# attempt to impute using nearest neighbors
x <- iris [, 1:4]
pp <- preProcess (x, method = c("knnImpute"))
x.imputed <- predict (pp, newdata = x)
# expect all NAs were populated with an imputed value
stopifnot( all (!is.na (x.imputed)))
stopifnot( length (x) == length (x.imputed))
答案 0 :(得分:4)
请参阅?predict.train
:
## S3 method for class 'train'
predict(object, newdata = NULL, type = "raw", na.action = na.omit, ...)
这里也有一个na.omit
:
> length(predict (fit, test))
[1] 29
> length(predict (fit, test, na.action = na.pass))
[1] 30
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