循环中来自 i 的 R 名称数据框

Question

我有以下代码，我想将由 sqldf 创建的数据框命名为 t2_value_of_i。然后我想将这些文件附加到一个文件中，推荐的方法是什么？下面的迭代在整个循环中覆盖为 t2_i。谢谢。

m4<-data.frame(m3[-1,])

colnames(m4)<-c("iteration_criteria")
m4$iteration_criteria<-as.character(m4$iteration_criteria)


m4.list <-vector("list", nrow(m4))


for (i in 1:nrow(m4)) {
  m4.list[[i]] <- m4[i,] }

for (i in m4.list){


t2_i<-sqldf(print(paste(
"select a.*, b.iteration_criteria
 from data_by_zone_final a left join t1 b  on
                  (a.state_long=b.state_long) and 
                  (a.state_short=b.state_short) and 
                  (a.state_subregion_name=b.state_subregion_name)
where (a.local_hour_final=17) and b.iteration_criteria='",m4.list,"'",sep="" )     ))
}

Answer 1

您可以使用paste或paste0结合assign更新变量名，如下：

final = c()
for (i in m4.list){
  temp <- assign(paste0('t2_', i), sqldf(print(paste(
    "select a.*, b.iteration_criteria
     from data_by_zone_final a left join t1 b  on
                      (a.state_long=b.state_long) and 
                      (a.state_short=b.state_short) and 
                      (a.state_subregion_name=b.state_subregion_name)
    where (a.local_hour_final=17) and b.iteration_criteria='",m4.list,"'",sep="" )     
  )))
  final <- rbind(final, temp)
}

Answer 2

如果你不需要中间结果，你可以马上rbind到你的最终对象：

final = c()
for (i in m4.list){
  temp = sqldf(print(paste(
    "select a.*, b.iteration_criteria
    from data_by_zone_final a left join t1 b  on
    (a.state_long=b.state_long) and 
    (a.state_short=b.state_short) and 
    (a.state_subregion_name=b.state_subregion_name)
    where (a.local_hour_final=17) and b.iteration_criteria='", i,"'",sep="" )     ))
  final = rbind(final, temp)
}