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rwindowtidy

Sliding dataset for x rows R

I have a dataset like the below and would like to create a nested dataframe for the last 20 rows.

x <- rep(1:100, 1)
y <- rnorm(100)
z <- rnorm(100)*2

data.frame(x,y,z)

For example, where x = 100 it would include the records for rows where x = 81:100, x = 99 would include 80:99 and so on. If there are not 20 rows before it would only include the number of rows before like 15 would include 1:15.

The ideal output would be nested so functions could be applied to all dataframes

Solution

  • If I've correctly understood, this function should fit:

    #library
library(tidyverse)

#data
x <- rep(1:100, 1)
y <- rnorm(100)
z <- rnorm(100)*2

dataf <- data.frame(x,y,z)

#working function
getDf <- function(df, n) {

  if (n >= 19) {

    return(df %>% slice((n-19):n))  

  } else {

    return(df %>% slice(1:n))

  }

}

#examples
getDf(dataf,100)

getDf(dataf,99)

getDf(dataf,15)