R -apply- 将许多列从数字转换为因子 [英] R -apply- convert many columns from numeric to factor

问题描述

我需要将许多数字列转换为因子类型.示例表:

I need to convert many columns that are numeric to factor type. An example table:

df <- data.frame(A=1:10, B=2:11, C=3:12)

我试过申请:

cols<-c('A', 'B')
df[,cols]<-apply(df[,cols], 2, function(x){ as.factor(x)});

但结果是一个字符类.

> class(df$A)
[1] "character"

如果不为每一列做 as.factor，我怎么能做到这一点?

How can I do this without doing as.factor for each column?

推荐答案

尝试

df[,cols] <- lapply(df[,cols],as.factor)

问题在于 apply() 试图将结果绑定到一个矩阵中，这导致将列强制为字符:

The problem is that apply() tries to bind the results into a matrix, which results in coercing the columns to character:

class(apply(df[,cols], 2, as.factor))  ## matrix
class(as.factor(df[,1]))  ## factor

相反，lapply() 对列表的元素进行操作.

In contrast, lapply() operates on elements of lists.

这篇关于R -apply- 将许多列从数字转换为因子的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！