如何使用dplyr同时交换两列中的值

Question

我有以下数据框：

df <- structure(list(sqn = c("FOO", "BAR"), start = c(1, 99), end = c(531, 
1), strand = c("+", "-")), row.names = c(NA, -2L), class = c("tbl_df", 
"tbl", "data.frame"))

看起来像：

# A tibble: 2 x 4
  sqn   start   end strand
  <chr> <dbl> <dbl> <chr> 
1 FOO       1   531 +     
2 BAR      99     1 -     

我想做的是交换if start和endcolumn中的值strand == "-"。期望的结果是这样的：

# A tibble: 2 x 4
  sqn   start   end strand
  <chr> <dbl> <dbl> <chr> 
1 FOO       1   531 +     
2 BAR       1    99 -   

我该如何实现？

Answer 1

一个选择是

df %>% 
  mutate(start1 = ifelse(strand == "-", end, start), 
         end = ifelse(strand =="-", start, end)) %>% 
  select(sqn, start = start1, end, strand)

或更简单的选择是

i1 <- df$strand == "-"
df[i1, c("start", "end")] <- df[i1, c("end", "start")]