R语言报错：Error in a1:a2 : NA/NaN argument

yijiaobani

8193

收藏 2015-08-12

悬赏 5 个论坛币已解决

我编写一个函数，出现报错：

Error in a1:a2 : NA/NaN argument，没有结果。

我把函数提取出来，处理，也出现同样的报错，但是有结果。

我的问题：

1、为什么报错？

2、为什么程序可以运行出结果，但是编程函数调用就没有结果，什么情况？

程序如下：

to<- c("a",23,3,5,4,"a",23,"a")
c<- NULL
hello <- function(a){
  total<- a
  location <- grep("a",total)
  for(a in seq(location)){
  a1 <- (location[a]+1) # near the up  number
  a2 <- (location[a+1]-1) # near the down number
  for (b in (a1:a2)){
c <- to[a]
  }
}
}
hello(to)

c

结果：
> hello(to)
Error in a1:a2 : NA/NaN argument
> c
NULL
这是调用函数的结果，c没有被处理，不明白。

单独运行程序：
to<- c("a",23,3,5,4,"a",23,"a")
c<- NULL
  total<- to
  location <- grep("a",total)
  for(a in seq(location)){
a1 <- (location[a]+1) # near the up ck number
a2 <- (location[a+1]-1) # near the down ck number
for (b in (a1:a2)){
   c <- to[a]
}
  }
c
结果如下：
> for(a in seq(location)){ a1 <- (location[a]+1) # near the up ck number
   a2 <- (location[a+1]-1) # near the down ck number
for (b in (a1:a2)){
   c <- to[a]
   }
}
Error in a1:a2 : NA/NaN argument
> c[1] NA "a"  "a"  "a"  "a"  NA "23"
这里c是有结果的，也出现报错信息：NA/NaN argument