Extract a value from a dataframe iteratively (R)

Question

I have a function to select a value from a dataframe. I want to select that value, save it, remove it from the dataset, and select a value using the same function from the remaining values in the dataframe. What is the best way to do this?

Here is a simple example:

V1 <- c(5,6,7,8,9,10)
df <- data.frame(V1)

V2 <- as.data.frame(matrix(nrow=3,ncol=1))

maximum <- function(x){
  max(x)
}

V2[i,]<- maximum(df)

df <- anti_join(df,V2,by='V1')

How can I set this up such that I reapply the maximum function to the remaining values in df and save these values in in V2?

I'm using a different and more complex set of functions and if/else statements than max - this is just an example. I do have to reapply the function to the remaining values, because I will be using the function on a new dataframe if df is empty.

Answer 1

Is this what you're looking for?

V1 <- data.frame(origin = c(5,6,7,8,9,10))

V2 <- as.data.frame(matrix(nrow=3,ncol=1))

df1 <- V1
df2 <- V2

recursive_function <- function(df1,df2,depth = 3,count = 1){
  
  if (count == depth){
    # Find index
    indx <- which.max(df1[,1])
    curVal <- df1[indx,1]
    
    df2[count,1] <- curVal
    
    df1 <- df1[-indx, ,drop = FALSE]
    
    return(list(df1,
                df2))
  } else {
    # Find index
    indx <- which.max(df1[,1])
    # Find Value
    curVal <- df1[indx,1]
    
    # Add value to new data frame
    df2[count,1] <- curVal
    
    # Subtract value from old dataframe
    df1 <- df1[-indx, ,drop = FALSE]
    
    recursive_function(df1,df2,depth,count + 1)
  }
}

recursive_function(df1,df2)