R: Function using if-statement only returning one else condition regardless of value

Question

Hey,

I have the following R function that checks a range of values and writes out a sentence about them. The problem is when I use the function and then call it all the sentences are the same regardless of Value.

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

Any ideas as to how to fix this problem.

Here is sample data:

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

Here is what I have at present:

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")

Hope this helps.

Answer 1

There are many problems with this :

1) you're using a function without arguments, and hope it does something with the variables in your global environment. That's dangerous.

2) the function isn't returning anything. Actually it is : it returns the last assignment, but I'm positive you're not aware of this, so in any case you better always include a return() clause.

3) an if() clause is not vectorized, so it only uses the first condition. In your case it only tests the first row of df.

5) && and || are used if you only want to test the first value of a series. The ones you need here is & and | (see ?"&" in R)

5) Don't call your dataframe df, df() is a function.

To do what I guess you want to do, try this :

#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