R - 将许多列从数字转换为因子 [英] R -apply- convert many columns from numeric to factor
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问题描述
我需要将许多列数字转换为因子类型。
示例表:
df < - data.frame(A = 1:10,B = 11,C = 3:12)
我尝试了apply:
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
$ p
<$ p $ p>
df [,cols]< - lapply(df [,cols],as.factor)
问题是 apply()
试图将结果绑定到一个矩阵中,这导致将列强制为字符:
class(apply(df [,cols],2,as.factor))## matrix
class(as.factor df [,1]))##因子
相反, lapply )
操作列表的元素。
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)
I tried with apply:
cols<-c('A', 'B')
df[,cols]<-apply(df[,cols], 2, function(x){ as.factor(x)});
But the result is a character class.
> class(df$A)
[1] "character"
How can I do this without doing as.factor for each column?
解决方案
Try
df[,cols] <- lapply(df[,cols],as.factor)
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
In contrast, lapply()
operates on elements of lists.
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