我试图从另一组中减去一组的值。我希望使用 tidyverse
structure(list(A = c(1, 1, 1, 2, 2, 2, 3, 3, 3), group = c("a",
"b", "c", "a", "b", "c", "a", "b", "c"), value = c(10, 11, 12,
11, 40, 23, 71, 72, 91)), class = "data.frame", row.names = c(NA,
-9L))
这是我的数据,我想从 B 和 C 中减去 A 组的所有值,并将差值存储在一个变量中。
答案 0 :(得分:2)
我只使用了 data.table 而不是 data.frame 因为我更熟悉。
library(data.table)
data <- setDT(structure(list(A = c(1, 1, 1, 2, 2, 2, 3, 3, 3), group = c("a",
"b", "c", "a", "b", "c", "a", "b", "c"), value = c(10, 11, 12,
11, 40, 23, 71, 72, 91)), class = "data.frame", row.names = c(NA,-9L)))
for (i in 1:length(unique(data$A))){
data[A == i, substraction := data[A == i, 'value'] - data[A == i & group == 'a', value]]
}
答案 1 :(得分:2)
baseR
解决方案
df$new <- df$value - ave(df$value, df$A, FUN = function(x) mean(x[df$group == 'a'], na.rm = T) )
> df
A group value new
1 1 a 10 0
2 1 b 11 1
3 1 c 12 2
4 2 a 11 0
5 2 b 40 29
6 2 c 23 12
7 3 a 71 0
8 3 b 72 1
9 3 c 91 20
dplyr
方法(假设每组不超过一个 a
值,否则 R 会混淆要减去哪个值并导致错误)
df %>% group_by(A) %>% mutate(new = ifelse(group != 'a', value - value[group == 'a'], value) )
# A tibble: 9 x 4
# Groups: A [3]
A group value new
<dbl> <chr> <dbl> <dbl>
1 1 a 10 10
2 1 b 11 1
3 1 c 12 2
4 2 a 11 11
5 2 b 40 29
6 2 c 23 12
7 3 a 71 71
8 3 b 72 1
9 3 c 91 20
或者如果您想更改所有值
df %>% group_by(A) %>% mutate(new = value - value[group == 'a'] )
# A tibble: 9 x 4
# Groups: A [3]
A group value new
<dbl> <chr> <dbl> <dbl>
1 1 a 10 0
2 1 b 11 1
3 1 c 12 2
4 2 a 11 0
5 2 b 40 29
6 2 c 23 12
7 3 a 71 0
8 3 b 72 1
9 3 c 91 20