我有一个数据集data
,包含66个变量和大约200,000个观测值。数据结构的快照如下所示:
$ f37: Factor w/ 10 levels "","1","10","2",..: 2 4 4 2 4 2 4 2 2 4 ...
$ f38: Factor w/ 3509 levels "","100","1000",..: 1 1 1 1 1 1 1 1 1 1 ...
$ f39: Factor w/ 15 levels "","1","11","14",..: 7 4 2 4 7 8 15 7 4 4 ...
$ f40: Factor w/ 15097 levels "","0","1","100",..: 11150 1 5539 1 6710 1650 14680 9235 1 1 ...
$ f41: num 2156 2156 2156 2156 2156 ...
$ f42: Factor w/ 14583 levels "","'0503624",..: 11573 1 13170 1 9243 8310 607 1979 1 1 ...
$ f43: Factor w/ 133655 levels ""," ","(BLANK)",..: 92730 1 2046 1 26944 65286 198 42956 1 1 ...
$ f44: Factor w/ 145029 levels "","-"," "," 1A8GHB1R76Y123913",..: 49912 1 14207 1 9798 121241 31872 88345 1 1 ...
$ f45: Factor w/ 124642 levels "","'11291331764964",..: 118266 1 108600 1 14814 3176 46466 99158 1 1 ...
$ f46: Factor w/ 6524 levels ""," "," HOL 232",..: 85 1 1 1 207 1 1 1 `
数据中有大量的分类变量。我想排除级别大于数字的分类变量, n 。这不仅可以减少计算时间,还可以确保某些机器学习算法(如随机森林)工作。
我尝试过以下代码:
drop_factors <- function(x){
for (j in 1:length(x[1,])) {
if (is.factor(x[,j])) {
if(nlevels(x[,j])>32){
x[,j]<-NULL
}
}
}
}
然而,当我尝试:
dropfactors(data)
我收到以下错误:
Error in `[.data.frame`(x, , j) : undefined columns selected
我真的很感激任何帮助?
答案 0 :(得分:0)
您不需要for循环:
data[sapply(data, nlevels) <= 32]
您收到错误是因为您在for循环期间更改了数据框的列数。因此,j
可能会采用大于剩余列数的值。
答案 1 :(得分:0)
你可以这样做,以确定超过32个级别的因素:
factor32 <- sapply(data, function(x) class(x) == "factor" & nlevels(x) > 32)
data <- data[, !factor32]
V