一次将多个列强制转换为因子 [英] Coerce multiple columns to factors at once

问题描述

我有一个如下示例数据框:

I have a sample data frame like below:

data <- data.frame(matrix(sample(1:40), 4, 10, dimnames = list(1:4, LETTERS[1:10])))

我想知道如何选择多个列并将它们一起转换为因子.我通常以 data$A = as.factor(data$A) 之类的方式进行操作.但是当数据框非常大并且包含很多列时，这种方式将非常耗时.有谁知道更好的方法吗?

I want to know how can I select multiple columns and convert them together to factors. I usually do it in the way like data$A = as.factor(data$A). But when the data frame is very large and contains lots of columns, this way will be very time consuming. Does anyone know of a better way to do it?

推荐答案

选择一些列强制转换为因子:

Choose some columns to coerce to factors:

cols <- c("A", "C", "D", "H")

使用 lapply() 强制和替换选定的列:

Use lapply() to coerce and replace the chosen columns:

data[cols] <- lapply(data[cols], factor)  ## as.factor() could also be used

检查结果:

sapply(data, class)
#        A         B         C         D         E         F         G 
# "factor" "integer"  "factor"  "factor" "integer" "integer" "integer" 
#        H         I         J 
# "factor" "integer" "integer" 

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