CODEWITHSUNDEEP
rfunctiondataframe
holdingOnByaString
holdingOnByaString

Reputation: 15

Trying to Make an R Function to Retrieve a Variable Name

I'm new to R and trying to create a function which I think should be fairly straight-forward but I'm stuck. I have a data frame with states and their populations for various years. I want to make a function which finds the highest population in a given year and returns the corresponding state name. I know how to retrieve the max population, but I don't know how to use that to look up the corresponding state name. Here's my code to find the max population:

max(dfStates$Jul2011)

Now, putting that into a function so far I have:

lotsOfPeeps<-function(dfStates){ highestPop<-max(dfStates$Jul2011) return(highestPop)}

So, when I run lotsOfPeeps(dfStates) right now it just returns the highest population value. How would I add to it to retrieve the state name?

Upvotes: 1

Views: 52

Answers (2)

NelsonGon
NelsonGon

Reputation: 13319

A variation to make the function more flexible. This will likely be slower than which.max.

lotsOfPeeps<-function(df, column,target_column){
  highestPop<-df[df[column]==max(df[column]),target_column]

  return(highestPop)
  }

To get it in "column-like" format, we can wrap highestPop in [[ as suggested by @akrun such that:

highestPop<-df[df[column]==max(df[column]),][target_column]

Testing with iris:

lotsOfPeeps(iris,"Sepal.Length","Species") # name maintained,can be better named
[1] virginica
Levels: setosa versicolor virginica

Result if highestPop is wrapped in [[:

lotsOfPeeps(iris,"Sepal.Length","Species")
      Species
132 virginica

Upvotes: 1

Ronak Shah
Ronak Shah

Reputation: 389235

Use which.max which will return index of the highest value of population and use it to get corresponding state name. Assuming the column with state name is called StateName, you can do 

lotsOfPeeps<-function(dfStates){
   hihest_pop_state <- dfStates$StateName[which.max(dfStates$Jul2011)]
   return(hihest_pop_state)
}

lotsOfPeeps(dfStates)

Upvotes: 1

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