根据条件创建具有值的新列

Question

我需要创建一个基于第三列的值列。示例：

df <- data.frame(antibodies = c("positive","positive","positive","positive",
                            "negative","negative","negative","negative",
                            "negative","positive","positive","negative"),
             AA = c(123, 345, 7567, 234, 8679, 890, 
                    812, 435345, 567, 568, 786, 678),
             stringsAsFactors = F)

我想要创建一个名为df$BB的新列，为了使这个列具有以下两个条件：

• ，如果抗体阳性，则BB= AA+2
• ，如果抗体为阴性，则BB== AA

我怎么用R来表达这个？

谢谢!

Answer 1

以下是一次尝试：

# Base R
df$BB <- ifelse(df$antibodies == "positive", df$AA + 2, df$AA)

# Dplyr
library(dplyr)
df <- df %>% 
  mutate(BB = if_else(antibodies == "positive", AA + 2, AA))

Answer 2

使用within。

df <- within(df, {
  BB <- AA
  BB[antibodies == "positive"] <- BB + 2
})
df
#    antibodies     AA     BB
# 1    positive    123    125
# 2    positive    345    347
# 3    positive   7567   7569
# 4    positive    234    236
# 5    negative   8679   8679
# 6    negative    890    890
# 7    negative    812    812
# 8    negative 435345 435345
# 9    negative    567    567
# 10   positive    568    570
# 11   positive    786    788
# 12   negative    678    678

Answer 3

使用base R的ifelse-function：

df$BB <- ifelse(df$antibodies=="positive", df$AA + 2, df$AA)

或与with相结合

df$BB <- with(df, ifelse(antibodies=="positive", AA + 2, AA))

返回

   antibodies     AA     BB
1    positive    123    125
2    positive    345    347
3    positive   7567   7569
4    positive    234    236
5    negative   8679   8679
6    negative    890    890
7    negative    812    812
8    negative 435345 435345
9    negative    567    567
10   positive    568    570
11   positive    786    788
12   negative    678    678

另一个解决办法是

df$BB <- as.numeric(df$antibodies == "positive") * 2 + df$AA