library(tidyverse);library(magritter)
data%>%arrange(fcn,COUNTRY)%>%filter(Vit_B6!=0)%>%group_by(fcn,COUNTRY)%>%mutate(Vit_B6_1=first(Vit_B6))%>%ungroup()->
data1

错了一个字符，下面这个是对的

library(tidyverse);library(magritte)
data%>%arrange(fcn,COUNTRY)%>%filter(Vit_B6!=0)%>%group_by(fcn,COUNTRY)%>%mutate(Vit_B6_1=first(Vit_B6))%>%ungroup()->
data1

你好，每种食物有4条数据，理想的结果是最后每个食物只保留一个国家的数据，跑了您的代码实现不了，数据的条数不对，好像就是把值为0的去掉了，我还希望能再生成一列，显示出取的数据的国家来源

楼上的答案其实差不多了，国家的排序可能需要多一个factor(levels = )的函数来完成，这里不细说，后面的我觉得是group的时候不需要纳入country，且既然已经按国家排序并去掉了0，直接slice取第一行即可
library(tidyverse);library(magritte)
data %>% arrange(fcn,COUNTRY)%>%filter(Vit_B6!=0)%>%group_by(fcn)%>%slice(1)%>%ungroup()->
data1

setwd("D:\\Vit_B")
rm(list=ls(all=TRUE))

if (!require("pacman", character.only = T, quietly = T)) {
  install.packages("pacman")
  library(pacman,character.only = T)
}
pacman::p_load(tidyverse,rio,magrittr,writexl)

rio::import(file="D:\\Vit_B\\data.xlsx") %>%
  mutate_at(.,vars(Vit_B6,Vit_B12),~replace(.,is.na(.),0)) %>%
  mutate(COUNTRY=ordered(COUNTRY,levels=c("CN","JP","UK","US"))) ->data
  #ordered factor
data %>% filter(Vit_B6!=0) %>%
  group_by(fcn) %>%
  summarise(.,Vit_B6_1=first(Vit_B6)) %>% ungroup %>%
  left_join(data) %>%
  filter(Vit_B6_1==Vit_B6)->Vit_B6_1

data %>% filter(Vit_B12!=0) %>%
  group_by(fcn) %>%
  summarise(.,Vit_B12_1=first(Vit_B12)) %>% ungroup %>%
  left_join(data) %>%
  filter(Vit_B12_1==Vit_B12)->Vit_B12_1

rio::import(file="D:\\Vit_B\\data.xlsx") %>%
  select(fcn) %>% distinct->fcn

fcn %>% left_join(Vit_B6_1) %>% left_join(Vit_B12_1) %>%
  mutate_at(.,vars(Vit_B6_1,Vit_B12_1),~replace(.,is.na(.),0)) %>%
  mutate(COUNTRY2="CN") %>%
  select(fcn,COUNTRY,Vit_B6_1,COUNTRY2,Vit_B12_1)->
  data_F

rio::export(data_F,file="D:\\Vit_B\\data_F.xlsx")
rio::export(x=data_F,which="data_F",
            file="D:\\Vit_B\\data.xlsx")

rm(list=ls())