# Getting started with runner

#### Dawid Kałędkowski

#### 2026-01-30

## About

Package contains standard running functions (aka. rolling) with additional options like varying window size, lagging, handling missings and windows depending on date. `runner` brings also rolling streak and rolling which, what extends beyond range of functions already implemented in R packages. This package can be successfully used to manipulate and aggregate time series or longitudinal data.

## Using runner

`runner` package provides functions applied on running windows. The most universal function is `runner::runner` which gives user possibility to apply any R function `f` in running window. In example below 4-months correlation is calculated lagged by 1 month.

    library(runner)

    x <- data.frame(
      date = seq.Date(Sys.Date(), Sys.Date() + 365, length.out = 20),
      a = rnorm(20),
      b = rnorm(20)
    )

    runner(
      x,
      lag = "1 months",
      k = "4 months",
      idx = x$date,
      f = function(x) {
        cor(x$a, x$b)
      }
    )

There are different kinds of running windows and all of them are implemented in `runner`.

## Running windows

Following diagram illustrates what running windows are - in this case running windows of length `k = 4`. For each of 15 elements of a vector each window contains current 4 elements.

### Window size

`k` denotes number of elements in window. If `k` is a single value then window size is constant for all elements of x. For varying window size one should specify `k` as integer vector of `length(k) == length(x)` where each element of `k` defines window length. If `k` is empty it means that window will be cumulative (like `base::cumsum`). Example below illustrates window of `k = 4` for 10th element of vector `x`.

    runner(1:15, k = 4)

### Window lag

`lag` denotes how many observations windows will be lagged by. If `lag` is a single value than it is constant for all elements of x. For varying lag size one should specify `lag` as integer vector of `length(lag) == length(x)` where each element of `lag` defines lag of window. Default value of `lag = 0`. Example below illustrates window of `k = 4` lagged by `lag = 2` for 10-th element of vector `x`. Lag can also be negative value, which shifts window forward instead of backward.

    runner(
      1:15,
      k = 4,
      lag = 2
    )