使用if语句的函数只返回一个else条件而不管value

Question

我有以下R函数,它检查一系列值并写出一个关于它们的句子.问题是,当我使用该函数然后调用它时,无论Value如何,所有句子都是相同的.

hover <- function (){
if(df$Value > 140 && df$Change < -0.05){
hovertext ="Price High, Level of Activity Low"
}else{
   if(df$Value < 140 && df$Change > 90 && df$YVoltage > -0.05 &&
      df$YVoltage < 0.30 ){
    hovertext ="Price Normal, Level of Activity normal"
      } else {
hovertext ="Price High, Level of Activity high"
      }
  }
}
hovertext <- hover ()
hovertext

关于如何解决这个问题的任何想法.

以下是示例数据:

TimeStamp,Price,Change
12:00:00,140,0.05
12:12:03,148,0.06
12:12:40,130,-0.05
12:12:50,135,0.01
12:13:00,135,0
12:13:10,1.37,0.01

这就是我目前所拥有的:

library (ggplot2)
df <- read.csv(file.choose(), header =TRUE) 
df
df$Price <- as.numeric(as.character(df$Price))
df$Change <- as.numeric(as.character(df$Change))
df$TimeStamp <- strptime(as.character(df$TimeStamp), "%H:%M:%OS")
sapply(df, class)          
options("digits.secs"=3)   
summary (df)              
df$TimeStamp <- df[1,"TimeStamp"] +
  cumsum(runif(1:length(df$TimeStamp))*60)
summary(df)
hover <- function (df){ 
    out <- ifelse((df$Value > 140 & df$Change < -0.05), 
              "Price High, Level of Activity Low", 
    ifelse((df$Value < 140 & df$Change > 90 && 
          df$YVoltage > -0.05 & df$Change < 0.30), 
              "Price Normal, Level of Activity normal", 
              "Price High, Level of Activity high" 
          )) 
    return(out) 
} 
hovertext <- hover(df) 
hovertext 

sink (file="c:/Users/user/text.txt", type="output",split=FALSE)
cat(sprintf("    Time=\"%s\" value=\"%f\" hoverText =\" %s\" ></set>\n",
            df$TimeStamp, df$Price, hovertext))
unlink("text.txt")

希望这可以帮助.

Answer 1

这有很多问题:

1)你正在使用一个没有参数的函数,并希望它对你的全局环境中的变量做一些事情.这很危险.

2)该功能没有返回任何东西.实际上它是:它返回最后一个赋值,但我很肯定你没有意识到这一点,所以无论如何你最好总是包含一个return()子句.

3)if()子句没有矢量化,因此它只使用第一个条件.在你的情况下,它只测试df的第一行.

5)&&并且||如果您只想测试系列的第一个值,则使用它.你需要的是&和|(参见?"&"R)

5)不要调用你的数据帧df,df()是一个函数.

要做我想你想做的事,试试这个:

#Sample data for testing
Df <- data.frame(Value = rnorm(100,140,10),
Change = rnorm(100,90,90),
YVoltage = rnorm(100,0.10,0.30))

hover <- function (X){
    out <- ifelse((X$Value > 140 & X$Change < -0.05),
              "Price High, Level of Activity Low",
    ifelse((X$Value < 140 & X$Change > 90 &
          X$YVoltage > -0.05 & X$YVoltage < 0.30),
              "Price Normal, Level of Activity normal",
              "Price High, Level of Activity high"
          ))
    return(out)
}

hovertext <- hover(Df)
hovertext