Question

在请求时，函数foo1可以subset列表by所需的变量（例如by = ESL == 1）。否则，foo1只会简单地输出输入列表本身。

出于我的目的，我需要在名为foo1的新函数中使用foo2。但我想知道foo2为何失败以及如何解决：

Error in eval(e, x, parent.frame()) : object 'ESL' not found

完整的可复制数据和代码如下：

foo1 <- function(by, data){

L <- split(data, data$study.name) ; L[[1]] <- NULL

 if(!missing(by)){

 s <- substitute(by)    

 H <- lapply(L, function(x) do.call("subset", list(x, s)))

 L <- Filter(nrow, H)
   }
return(L)
}

## EXAMPLE OF USE:
D <- read.csv("https://raw.githubusercontent.com/izeh/i/master/k.csv", h = T) ## Data

foo1(data = D, by = ESL == 1) ## works fine :-) @@@@

## BUT:
foo2 <- function(by, data){

  foo1(by = by, data = data)
}

## EXAMPLE OF USE:
foo2(data = D, by = ESL == 1) ## Fails :-( @@@@

Answer 1

在这里，我们可以将foo2修改为eval来完善函数调用

foo2 <- function(by, data){ 

  eval(substitute(foo1(by = by, data = data)))
 }

out1 <- foo1(data = D, by = ESL == 1) 
out2 <- foo2(data = D, by = ESL == 1) 
identical(out1, out2)
#[1] TRUE

在辅助R函数中使用`subset（）`

1 个答案: