在R中输出数据帧的函数

Question

I have an example data frame named df :

    Store    Cash Only 
1    "A"      Y
2    "B"      N
3    "C"      N
4    "D"      Y 

I would like to create a function that allows a user to see whether or not a store is "cash only". Ideally, the function would output only the stores that have a Y in the Cash Only column. The output should look like this:

  Store    Cash Only 
1    "A"      Y
2    "D"      Y 

Does anyone know how I would go about this? Thanks!

Answer 1

you just need to write a function that returns a subset of the input dataframe where cash == "Y" :

df = data.frame(store=c("a","b","c","d"), cash=c("Y","N","N","Y"))

cash_only <- function(df){
  return(subset(df, cash == "Y"))
}

new_df <- cash_only(df)

Answer 2

This function gives you more flexibility,

select_sub_dataframe<-function(df,colname,value){ return(df[df[,colname]==value,]) }

You can call this function and get the subset by

select_sub_dataframe(df,"Cash Only","Y")