Question

我有一个带足球位置缩写的因子栏，大约17个独特的值，有220个观察值。我想只有三个因子级别，包含17个唯一值。

levels(nfldraft$Pos) <- list(Linemen = c("C","OG","OT","TE","DT","DE"), Small_Backs =  c("CB","WR","FS"), Big_Backs = c("FB","ILB","OLB","P","QB","RB","SS","WR"))

是我尝试的，打印nfldraft$Pos到控制台显示3个因子级别，但所有值都是Linemen或Small_Backs，所有其他值都是NA。我哪里错了？谢谢

Answer 1

我制作了一个包含所有缩写的示例字符向量：

my_example <- c("C","OG","OT","TE","DT","DE","CB","WR","FS", 
                "FB","ILB","OLB","P","QB","RB","SS","WR")
class(my_example)

[1]＆＃34;字符＆＃34;

然后我用他们的缩写替换了所需的级别（你也可以在这里使用gsub或许多不同的方法中的任何一种）：

my_example[my_example %in% c("C","OG","OT","TE","DT","DE")] <- "Linemen"
my_example[my_example %in% c("CB","WR","FS")]               <- "Small Backs"
my_example[my_example %in% c("FB","ILB","OLB","P",
                             "QB","RB","SS","WR")]          <- "Big Backs"

然后我把它变成了一个因素：

my_example <- as.factor(my_example)
head(my_example)

[1] Linemen Linemen Linemen Linemen Linemen Linemen
Levels: Big Backs Linemen Small Backs

tail(my_example)

[1] Big Backs   Big Backs   Big Backs   Big Backs   Big Backs   Small Backs
Levels: Big Backs Linemen Small Backs

class(my_example)

[1]＆＃34; factor＆＃34;

Answer 2

这是一个需要完全可复制的示例的好示例。实际上，OP的代码看起来看起来应该可以工作。从@ Hack-R的示例输入中获取：

my_example <- c("C","OG","OT","TE","DT","DE","CB","WR","FS", 
                "FB","ILB","OLB","P","QB","RB","SS","WR")

OP的原始代码按原样工作：

nfldraft = list(Pos = factor(my_example))
levels(nfldraft$Pos) <- list(
  Linemen = c("C","OG","OT","TE","DT","DE"), 
  Small_Backs =  c("CB","WR","FS"), 
  Big_Backs = c("FB","ILB","OLB","P","QB","RB","SS","WR")
)
table(nfldraft$Pos)
#     Linemen Small_Backs   Big_Backs 
#           6           2           9

这与如何使用levels<-的文档完全一致：

levels(x) <- value

value是levels(x)的有效值...对于factor方法，长度至少为x的层数的字符串向量，或指定如何重命名级别。

所以看来OP的输入还有其他问题

Answer 3

您还可以使用dplyr软件包中的 mapvalues（）函数。

在您的示例中为：

Linemen_levels = c("C","OG","OT","TE","DT","DE")
Small_Backs_levels = c("CB","WR","FS")
Big_Backs_levels = c("FB","ILB","OLB","P","QB","RB","SS","WR")

nfldraft <- nfldraft %>% mutate(Pos=mapvalues(Pos, 
                 from = c(Linemen_levels, Small_Backs_levels, Big_Backs_levels),
                 to = c(rep('Linemen', length(Linemen_levels), rep('Small_Backs', length(Small_Backs_levels), rep('Big_Backs', length(Big_Backs_levels))))))

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3 个答案: