r - quantregForest x 不包含数据

Question

运行此代码：

library(datasets)
library(quantregForest)

Xtrain <- iris$Sepal.Length
Ytrain <- iris$Petal.Width

model <- quantregForest(
    x = Xtrain
    , y = Ytrain
)

但收到此错误消息：

Error in quantregForest(x = Xtrain, y = Ytrain) :  x contains no data

谁能看看有什么问题？

PS：

这虽然有效：

library(datasets)
library(quantregForest)
library(dplyr)

Xtrain <- iris %>%
    select(
        Sepal.Length
        , Petal.Length
    )

Ytrain <- iris$Petal.Width

model <- quantregForest(
    x = Xtrain
    , y = Ytrain
)

标签： r