在执行函数之前验证参数

Question

我想验证我传递给函数的两个参数是否有效。

为此，我正在检查我分配给“state”变量的“State”值是否在状态列表“statelist”中。然后我检查我分配给我的“测量”变量的“测量”值是否在我的测量列表“测量列表”中。如果第一次检查失败，则应生成“无效状态”错误消息。如果第二次检查失败，则应生成“无效测量”错误消息。如果两项检查都通过，我希望函数最低

这是我的数据框，“数据”：

school<-c("NYU", "BYU", "USC", "FIT", "Oswego","UCLA","USF","Columbia")
state<-c("NY","UT","CA","NY","NY","CA", "CA","NY")
measure<-c("MSAT","MSAT","GPA","MSAT","MSAT","GPA","GPA","GPA")
score<-c(590, 490, 2.9, 759, 550, 1.2, 3.1, 3.2)
data<-data.frame(school,state, measure,score)

这个函数检查我有一个有效的州缩写：

teststate<-function(state){
  statelist<-(c(state.abb,"DC","GU","MP","PR","VI"))
  if(state %in% statelist){
    testmeasure(measure)
  } else{
    stop("invalid state")
  }
 } 

此函数检查我指定的度量值是否在我的度量值列表中：

testmeasure<-function(measure){ 
    measurelist<-c("MSAT","GPA","VSAT")
    if(measure %in% measurelist){
      lowest(state, measure)
    } else{
      stop("invalid measure")
    }
  }

这是有效性检查成功后应该运行的主要功能：

lowest <- function(state, measure){
    answer<-subset(data,subset=(state==State & measure==Measure))
    order.answer<-order(answer$score,answer$school)
    answer1<-as.matrix(answer[order.answer,])
    answer1[1,1]
  }

对于这个例子：

lowest("NY","MSAT")

正确答案应该是[1]“Owsego”，但是当我完整运行代码时，它永远不会完成，控制台只是显示：

+ lowest("NY","MSAT")
+ 

当我在函数之外独立测试每个模块时，它们都可以工作。

Answer 1

试试这个：

lowestV2 <- function(State,Measure){
  ##
  if(State %in% c(state.abb,"DC","GU","MP","PR","VI")){
    if(Measure %in% c("MSAT","GPA","VSAT")){
      answer<-subset(data,subset=(state==State & measure==Measure))
      order.answer<-order(answer$score,answer$school)
      answer1<-as.matrix(answer[order.answer,])
      answer1[1,1]
    } else {
      stop("invalid measure")
    }
  } else {
    stop("invalid state")
  }
  ##
}
##
> lowestV2("NY","MSAT")
[1] "Oswego"

除非您针对某种类型的复杂情况/条件进行错误捕获，否则您最好将处理直接包含在主函数中，而不是为每个条件调用外部错误处理函数。

Answer 2

可以使用checkmate 包（来自CRAN）进行参数检查。

加载数据：

school <- c("NYU", "BYU", "USC", "FIT", "Oswego","UCLA","USF","Columbia")
stateList <- c("NY","UT","CA","NY","NY","CA", "CA","NY")
measureList <- c("MSAT","MSAT","GPA","MSAT","MSAT","GPA","GPA","GPA")
score <- c(590, 490, 2.9, 759, 550, 1.2, 3.1, 3.2)
data <- data.frame(school, stateList, measureList, score)

加载包，并为函数添加测试：

library(checkmate)

lowest <- function (State, Measure) {
  expect_subset(State, stateList, empty.ok=FALSE, info="invalid state")
  expect_subset(Measure, measureList, empty.ok=FALSE, info="invalid measure")

  # if you also want to restrict to single states and measures
  assert_atomic(State, len=1)
  assert_atomic(Measure, len=1)

  answer<-subset(data,subset=(stateList==State & measureList==Measure))
  order.answer<-order(answer$score,answer$school)
  answer1<-as.matrix(answer[order.answer,])
  answer1[1,1]
}

测试我们的新功能：

lowest("NY","MSAT")
# [1] "Oswego"
lowest("NJ","MSAT")
# Error with message 'invalid state'
lowest("NY","blah")
# Error with message 'invalid measure'

Answer 3

我相信这个功能可以完成你想要的：

school<-c("NYU", "BYU", "USC", "FIT", "Oswego","UCLA","USF","Columbia")
state<-c("NY","UT","CA","NY","NY","CA", "CA","NY")
measure<-c("MSAT","MSAT","GPA","MSAT","MSAT","GPA","GPA","GPA")
score<-c(590, 490, 2.9, 759, 550, 1.2, 3.1, 3.2)
data<-data.frame(school,state, measure,score)

lowest <- function(State, Measure,Statelist,Measurelist,Data){
  if (!State%in%Statelist){
    stop("invalid state")
  }
  if (! Measure%in%Measurelist){
    stop("invalid measure")
  }
  else{
    answer<-subset(data,subset=(state==State & measure==Measure))
    order.answer<-order(answer$score,answer$school)
    answer1<-as.matrix(answer[order.answer,])
    print(answer1[1,1])
  }
}

lowest("NY","MSAT",state,measure,data)

它还使您能够在不更改函数本身的情况下为函数提供不同的状态、度量和数据集列表。