有條件地將因子水平分為兩個不同的水平

Question

我有一個數據框，例如：

df <- data.frame(
        type = c("BND", "INV", "BND", "DEL", "TRA"),
        chrom1 = c(1, 1, 1, 1, 1),
        chrom2 = c(1, 1, 2, 1, 3)
        )

我想將所有df[df$type=='BND',]實例重新分配給INV或TRA具體取決於chrom1和chrom2的值。

我試圖用fct_recode從forcats包像這樣：

library(forcats)

df$type <- ifelse(df$type=="BND", 
                  ifelse(df$chrom1 == df$chrom2,
                         fct_recode(df$type, BND="INV"),
                         fct_recode(df$type, BND="TRA")),
                  df$type)

但是，這將我的因素重新編號為數字：

  type chrom1 chrom2
1    1      1      1
2    3      1      1
3    1      1      2
4    2      1      1
5    4      1      3

這是我的預期結果：

  type chrom1 chrom2
1    INV      1      1 # BND -> INV as chrom1==chrom2
2    INV      1      1
3    TRA      1      2 # BND -> TRA as chrom1!=chrom2
4    DEL      1      1
5    TRA      1      3

如何以這種方式將因子分成兩個級別？

Answer 1

我的思考方式如下：（1）索引要更改的行，（2）執行ifelse語句。 我希望這有幫助：

  df <- data.frame(
  type = c("BND", "INV", "BND", "DEL", "TRA"),
  chrom1 = c(1, 1, 1, 1, 1),
  chrom2 = c(1, 1, 2, 1, 3)
)

indexBND<-which(df$type=="BND")
df$type[indexBND]<-ifelse(df$chrom1[indexBND] == df$chrom2[indexBND], df$type[indexBND] <- "INV", "TRA")

df
#   type chrom1 chrom2
# 1  INV      1      1
# 2  INV      1      1
# 3  TRA      1      2
# 4  DEL      1      1
# 5  TRA      1      3

干杯!

Answer 2

你也可以用case_when()

library(tidyverse)

df %>% 
  mutate(type = as.factor(case_when(
    type == 'BND' & chrom1 == chrom2 ~ 'INV', 
    type == 'BND' & chrom1 != chrom2 ~ 'TRA',
    TRUE  ~ as.character(type))))

數據：

df <- data.frame(
  type = c("BND", "INV", "BND", "DEL", "TRA"),
  chrom1 = c(1, 1, 1, 1, 1),
  chrom2 = c(1, 1, 2, 1, 3)
)

Answer 3

為了完整起見，這里也是一個簡潔的data.table解決方案：

library(data.table)
setDT(df)[type == "BND" & chrom1 == chrom2, type := "INV"][type == "BND", type := "TRA"][]

  type chrom1 chrom2 1: INV 1 1 2: INV 1 1 3: TRA 1 2 4: DEL 1 1 5: TRA 1 3 

好處是type 通過引用更新，例如，不復制整個對象，並且僅適用於條件適用的那些行。

Answer 4

要不就

df$type[df$type == "BND"] <- with(df, 
                                  ifelse(df[type == "BND", ]$chrom1 == 
                                           df[type == "BND", ]$chrom2,
                                         "INV", "TRA"))
> df
  type chrom1 chrom2
1  INV      1      1
2  INV      1      1
3  TRA      1      2
4  DEL      1      1
5  TRA      1      3