dvthis

The goal of dvthis is to provide utility functions for DVC pipelines using R scripts. An additional goal is to document the usual workflows they enable, and provide a template for projects using DVC and R.

Installation

You can install the current development version of dvthis with

remotes::install_github("jcpsantiago/dvthis")

No version available in CRAN yet.

Using dvthis

You can use DVC by itself by running dvc init within a git repo dir (read their docs here) and then use the utility functions to make your life easier. Or, you can use dvthis to setup the scaffolding for you.

• Create a new R (RStudio) project based on the dvthis template. It will have the following folder structure and initiate DVC for you (DVC must be installed on your system):

.
├── data               # all data that's not a model, metrics or plots goes here
│  ├── intermediate    # outputs of each stage to be used in future stages
│  └── raw             # original data; should never be overwritten; saved in remote storage with DVC
├── metrics            # metrics of interest in JSON; DVC can track these over time
├── models             # final output of your pipeline, in case it's a model
├── plots              # any plots produced, including CSVs with data for plots (see DVC docs)
├── queries            # .sql files or other format so that queries are also tracked
├── R                  # additional R functions needed for this project and not in a pkg yet
├── reports            # more complete reports or model cards
└── stages             # scripts for each stage; doesn't need to be only in R!

This structure assumes a DVC pipeline for Machine Learning made out of multiple stages/*.R which will

• take some data e.g. from a database using queries/*.sql
• save that data as data/raw/*.csv
• do something with it and save the intermediate steps as data/intermediate/*.qs
• finally output models/*, some metrics/*.json and plots/*.png

You are free, of course, to use your own naming conventions, stages, etc. E.g. maybe you don't have data coming from a database -- just delete the queries dir, and instead place your data in data/raw. Bam!

Since this is an R package, the examples focus on R scripts, but DVC does not care about languages. I have mixed Clojure and R, for example, without ill effects.

Stages

Stages should be small and focused, just like you would write your normal R functions. You can add a new R stage using the add_r_stage funciton. For example you could have stages (separate, independent scripts) for:

• Fetching data
• Cleaning data
• Feature transformation
• Train-test split
• Hyperparameter tuning
• Train final model
• Produce metrics
• Produce plots

This way it's possible to experiment and make changes to a smaller amount of code each time. It also enables an interactive workflow e.g. if you want to experiment with a new transformation

• Open the feature transformation script
• Run the read_intermediate_data() lines to load cached data the stage depends on
• Add a new transformation to e.g. a mutate()
• Run the modified chunk of code and see the result in the R REPL/Console
• Save the script and run dvc repro in the terminal to run the pipeline starting at the modified feature transformation script all the way downstream
• Rinse and repeat!

A stage script could look something like this:

#!/usr/bin/env Rscript

# you may not need command line arguments, but they're helpful in parameterised pipelines
n_of_dragons <- commandArgs(trailingOnly = TRUE)[1]

# assigning it to this_stage by convention will allow stage_footer() to be called without args
this_stage <- dvthis::stage_header("Choosing dragons")

dvthis::log_stage_step("Loading dragon data")
dragons_raw <- dvthis::read_raw_data("dragons.csv", readr::read_csv)

dvthis::log_stage_step("Loading clean kingdom data")
kingdoms <- dvthis::read_intermediate_result("kingdoms")

dvthis::log_stage_step("Keeping only {n_of_dragons} dragons")
dragons_clean <- head(dragons_raw, n_of_dragons)
dragons_and_kingdoms <- dplyr::inner_join(dragons_clean, kingdoms)

# you don't have to save every single intermediate result, but here I want to 
# be extensive for documentation sake
dvthis::log_stage_step("Saving intermediate dragons_clean")
dvthis::save_intermediate_result(dragons_clean)

dvthis::log_stage_step("Saving intermediate dragons_clean")
dvthis::save_intermediate_result(dragons_and_kingdoms)

dvthis::stage_footer()

RStudio Addins

dvthis also packs RStudio addins with shortcuts to commonly used DVC commands. I find it useful to bind these to keyboard shortcuts:

• Repro will run dvc repro.
• Repro until currently open stage will run all upstream stages on which the currently open stage script depends.

Contributing

Everyone has their prefered way of working, so maybe dvthis is not doing exactly what you need. Let me know! I'll also gladly review any feature or bug PRs :)