我的问题是关于在data.frame中的每对组之间执行计算,我希望它能被向量化。
我有一个data.frame,它由以下几列组成:Location
,Sample
,Var1
和Var2
。我想为Sample
和Location
的每一对Var1
找到每个Var2
的壁橱匹配。
我可以在一对位置上做到这一点,
df0 <- data.frame(Location = rep(c("A", "B", "C"), each =30),
Sample = rep(c(1:30), times =3),
Var1 = sample(1:25, 90, replace =T),
Var2 = sample(1:25, 90, replace=T))
df00 <- data.frame(Location = rep(c("A", "B", "C"), each =30),
Sample = rep(c(31:60), times =3),
Var1 = sample(1:100, 90, replace =T),
Var2 = sample(1:100, 90, replace=T))
df000 <- rbind(df0, df00)
df <- sample_n(df000, 100) # data
dfl <- df %>% gather(VAR, value, 3:4)
df1 <- dfl %>% filter(Location == "A")
df2 <- dfl %>% filter(Location == "B")
df3 <- merge(df1, df2, by = c("VAR"), all.x = TRUE, allow.cartesian=TRUE)
df3 <- df3 %>% mutate(DIFF = abs(value.x-value.y))
result <- df3 %>% group_by(VAR, Sample.x) %>% top_n(-1, DIFF)
我尝试了其他可能性,例如使用dplyr::spread
,但无法避免出现“错误:行的重复标识符”或用NA填充一半的列。
对于每个可能的组对,是否有更干净,更自动化的方法?我想避免每对手工的子集和合并例程。
答案 0 :(得分:1)
一种选择是使用“ combn
”创建“位置”的成对组合,然后按照OP的代码进行其他步骤
library(tidyverse)
df %>%
# get the unique elements of Location
distinct(Location) %>%
# pull the column as a vector
pull %>%
# it is factor, so convert it to character
as.character %>%
# get the pairwise combinations in a list
combn(m = 2, simplify = FALSE) %>%
# loop through the list with map and do the full_join
# with the long format data df1
map(~ full_join(df1 %>%
filter(Location == first(.x)),
df1 %>%
filter(Location == last(.x)), by = "VAR") %>%
# create a column of absolute difference
mutate(DIFF = abs(value.x - value.y)) %>%
# grouped by VAR, Sample.x
group_by(VAR, Sample.x) %>%
# apply the top_n with wt as DIFF
top_n(-1, DIFF))
此外,正如OP所提到的,有关自动接机而不是进行两次filter
(不过不清楚预期的输出)
df %>%
distinct(Location) %>%
pull %>%
as.character %>%
combn(m = 2, simplify = FALSE) %>%
map(~ df1 %>%
# change here i.e. filter both the Locations
filter(Location %in% .x) %>%
# spread it to wide format
spread(Location, value, fill = 0) %>%
# create the DIFF column by taking the differene
mutate(DIFF = abs(!! rlang::sym(first(.x)) -
!! rlang::sym(last(.x)))) %>%
group_by(VAR, Sample) %>%
top_n(-1, DIFF))