如何从R中的RandomForest中提取节点大小默认值

Question

我知道如何更改RandomForest中nodesize(终端节点中的最小行数(的值。然而，我想知道给定一个RandomForest模型，nodesize的值是多少。

require(party)
require (data.table)
require (e1071)
require (randomForest)
dat1 <- fread('https://archive.ics.uci.edu/ml/machine-learning-databases/abalone/abalone.data',stringsAsFactors=T)
## split data to train and test
set.seed(123)
dat1 <- subset(dat1, !is.na(V1))
smp_size<-0.8*nrow(dat1)
train_ind <- sample(seq_len(nrow(dat1)), size = smp_size)
train <- dat1[train_ind, ]
test <- dat1[-train_ind, ]
rf1 <- randomForest(V1 ~ ., data = train,keep.inbag = TRUE)
rf2 <- randomForest(V1 ~ ., data = train, ntree = 50,keep.inbag = TRUE)

Answer 1

碰巧randomForest没有返回节点大小参数。然而，它只有"三个"可能的值：要么由用户指定，要么由if (!is.null(y) && !is.factor(y)) 5 else 1设置(1用于分类，5用于回归(。因此，我们有

getNodesize <- function(x) {
look <- pmatch(names(x$call), "nodesize")
if(any(!is.na(look)))
x$call[!is.na(look)][[1]]
else if (!is.null(x$y) && !is.factor(x$y))
5
else
1
}
rf1 <- randomForest(V1 ~ ., data = train)
getNodesize(rf1)
# [1] 1
rf1 <- randomForest(V1 ~ ., data = train, nodesi = 3)
getNodesize(rf1)
# [1] 3