README.md

butterfly

The goal of butterfly is to aid in the verification of continually updating and overwritten time-series data, where we expect new values over time, but want to ensure previous data remains unchanged.

An illustration of continually updating timeseries data where a previous value unexpectedly changes.

Data previously recorded could change for a number of reasons, such as discovery of an error in model code, a change in methodology or instrument recalibration. Monitoring data sources for these changes is not always possible.

Unnoticed changes in previous data could have unintended consequences, such as invalidating a published dataset’s Digital Object Identfier (DOI), or altering future predictions if used as input in forecasting models.

This package provides functionality that can be used as part of a data pipeline, to check and flag changes to previous data to prevent changes going unnoticed.

Installation

You can install the development version of butterfly from GitHub with:

# install.packages("devtools")
devtools::install_github("thomaszwagerman/butterfly")

Overview

The butterfly package contains the following:

• butterfly::loupe() - examines in detail whether previous values have changed, and returns TRUE/FALSE for no change/change.
• butterfly::catch() - returns rows which contain previously changed values in a dataframe.
• butterfly::release() - drops rows which contain previously changed values, and returns a dataframe containing new and unchanged rows.
• butterfly::create_object_list() - returns a list of objects required by all of loupe(), catch() and release(). Contains underlying functionality.
• butterflycount - a list of monthly dataframes, which contain fictional butterfly counts for a given date.

Examples

This is a basic example which shows you how to use butterfly:

library(butterfly)

# Imagine a continually updated dataset that starts in January and is updated once a month
butterflycount$january
#>         time count
#> 1 2024-01-01    22
#> 2 2023-12-01    55
#> 3 2023-11-01    11

# In February an additional row appears, all previous data remains the same
butterflycount$february
#>         time count
#> 1 2024-02-01    17
#> 2 2024-01-01    22
#> 3 2023-12-01    55
#> 4 2023-11-01    11

# In March an additional row appears again
# ...but a previous value has unexpectedly changed
butterflycount$march
#>         time count
#> 1 2024-03-01    23
#> 2 2024-02-01    17
#> 3 2024-01-01    22
#> 4 2023-12-01    55
#> 5 2023-11-01    18

We can use butterfly::loupe() to examine in detail whether previous values have changed.

butterfly::loupe(
  butterflycount$february,
  butterflycount$january,
  datetime_variable = "time"
)
#> The following rows are new in 'df_current': 
#>         time count
#> 1 2024-02-01    17
#> ✔ And there are no differences with previous data.
#> [1] TRUE

butterfly::loupe(
  butterflycount$march,
  butterflycount$february,
  datetime_variable = "time"
)
#> The following rows are new in 'df_current': 
#>         time count
#> 1 2024-03-01    23
#> 
#> ℹ The following values have changes from the previous data.
#> old vs new
#>            count
#>   old[1, ]    17
#>   old[2, ]    22
#>   old[3, ]    55
#> - old[4, ]    18
#> + new[4, ]    11
#> 
#> `old$count`: 17 22 55 18
#> `new$count`: 17 22 55 11
#> [1] FALSE

butterfly::loupe() uses dplyr::semi_join() to match the new and old objects using a common unique identifier, which in a timeseries will be the timestep. waldo::compare() is then used to compare these and provide a detailed report of the differences.

butterfly follows the waldo philosophy of erring on the side of providing too much information, rather than too little. It will give a detailed feedback message on the status between two objects.

Using butterfly for data wrangling

You might want to return changed rows as a dataframe, or drop them altogether. For this butterfly::catch() and butterfly::release() are provided.

Here, butterfly::catch() only returns rows which have changed from the previous version. It will not return new rows.

df_caught <- butterfly::catch(
  butterflycount$march,
  butterflycount$february,
  datetime_variable = "time"
)
#> The following rows are new in 'df_current': 
#>         time count
#> 1 2024-03-01    23
#> 
#> ℹ The following values have changes from the previous data.
#> old vs new
#>            count
#>   old[1, ]    17
#>   old[2, ]    22
#>   old[3, ]    55
#> - old[4, ]    18
#> + new[4, ]    11
#> 
#> `old$count`: 17 22 55 18
#> `new$count`: 17 22 55 11
#> 
#> ℹ Only these rows are returned.

df_caught
#>         time count
#> 1 2023-11-01    18

Conversely, butterfly::release() drops all rows which had changed from the previous version. Note it retains new rows, as these were expected.

df_released <- butterfly::release(
  butterflycount$march,
  butterflycount$february,
  datetime_variable = "time"
)
#> The following rows are new in 'df_current': 
#>         time count
#> 1 2024-03-01    23
#> 
#> ℹ The following values have changes from the previous data.
#> old vs new
#>            count
#>   old[1, ]    17
#>   old[2, ]    22
#>   old[3, ]    55
#> - old[4, ]    18
#> + new[4, ]    11
#> 
#> `old$count`: 17 22 55 18
#> `new$count`: 17 22 55 11
#> 
#> ℹ These will be dropped, but new rows are included.

df_released
#>         time count
#> 1 2024-03-01    23
#> 2 2024-02-01    17
#> 3 2024-01-01    22
#> 4 2023-12-01    55

Relevant packages and functions

The butterfly package was created for a specific use case of handling continuously updating/overwritten time-series data, where previous values may change without notice.

There are other R packages and functions which handle object comparison, which may suit your specific needs better. Below we describe their overlap and differences to butterfly:

• waldo - butterfly uses waldo::compare() in every function to provide a report on difference. There is therefore significant overlap, however butterfly builds on waldo by providing the functionality of comparing objects where we expect some changes, with previous versions but not others. butterfly also provides extra user feedback to provide clarity on what it is and isn’t comparing, due to the nature of comparing only “matched” rows.
• diffdf - similar to waldo, but specifically for data frames, diffdf provides the ability to compare data frames directly. We could have used diffdf::diffdf() in our case, but we prefer waldo’s more explicit and clear user feedback. That said, there is significant overlap in functionality: butterfly::loupe() and diffdf::diffdf_has_issues() both provide a TRUE/FALSE difference check, while diffdf::diffdf_issue_rows() and butterfly::catch() both return the rows where changes have occurred. However, it lacks the flexibility of butterfly to compare object where we expect some changes, but not others.
• assertr - assertr provides assertion functionality that can be used as part of a pipeline, and test assertions on a particular dataset, but it does not offer tools for comparison. We do highly recommend using assertr for checks, prior to using butterfly, as any data quality issues will be caught first.
• daquiri - daquiri provides tools to check data quality and visually inspect timeseries data. It is also quality assurance package for timeseries, but has a very different purpose to butterfly.

Other functions include all.equal() (base R) or dplyr’s setdiff().

butterfly in production

Read more about how butterfly is used in an operational data pipeline to verify a continually updated and published dataset.