---
title: "Dataset (data frame) manipulation API for the tech.ml.dataset library"
output:
    md_document:
        variant: gfm
---

```{r setup, include=FALSE}
find_nrepl_port_up <- function() {
    wd <- getwd()
    while(wd != dirname(wd)) {
        f <- paste0(wd,"/.nrepl-port")
        if(file.exists(f)) return(paste0("@",f))
        wd <- dirname(wd)
        f <- NULL
    }
}
port_file <- find_nrepl_port_up()
if(is.null(port_file)) stop("nREPL port not found")
library(knitr)
knitr_one_string <- knitr:::one_string
nrepl_cmd  <- "rep"
opts_chunk$set(comment=NA, highlight=TRUE)
knit_engines$set(clojure = function(options) {
    rep_params <- if(isTRUE(options$stdout_only)) {
                      "--print 'out,1,%{out}' --print 'value,1,' -p"
                  } else {
                      "-p"
                  }
    code <- paste(rep_params, port_file, shQuote(knitr_one_string(options$code)))
    out <- if (options$eval) {
               if (options$message) message('running: ', nrepl_cmd, ' ', code)
               tryCatch(
                   system2(nrepl_cmd, code, stdout = TRUE, stderr = TRUE, env = options$engine.env),
                   error = function(e) {
                       if (!options$error) stop(e)
                       paste('Error in running command', nrepl_cmd)
                   }
               )
           } else ''
    if (!options$error && !is.null(attr(out, 'status'))) stop(knitr_one_string(out))
    engine_output(options, options$code, out)})
```

[![](https://img.shields.io/clojars/v/scicloj/tablecloth)](https://clojars.org/scicloj/tablecloth)
[![](https://api.travis-ci.org/scicloj/tablecloth.svg?branch=master)](https://travis-ci.org/github/scicloj/tablecloth)
[![](https://img.shields.io/badge/zulip-discussion-yellowgreen)](https://clojurians.zulipchat.com/#narrow/stream/236259-tech.2Eml.2Edataset.2Edev/topic/api)

## Versions

### tech.ml.dataset 7.x (master branch)

[![](https://img.shields.io/clojars/v/scicloj/tablecloth)](https://clojars.org/scicloj/tablecloth)

### tech.ml.dataset 4.x (4.0 branch)

`[scicloj/tablecloth "4.04"]`

## Introduction

[tech.ml.dataset](https://github.com/techascent/tech.ml.dataset) is a great and fast library which brings columnar dataset to the Clojure. Chris Nuernberger has been working on this library for last year as a part of bigger `tech.ml` stack.

I've started to test the library and help to fix uncovered bugs. My main goal was to compare functionalities with the other standards from other platforms. I focused on R solutions: [dplyr](https://dplyr.tidyverse.org/), [tidyr](https://tidyr.tidyverse.org/) and [data.table](https://rdatatable.gitlab.io/data.table/).

During conversions of the examples I've come up how to reorganized existing `tech.ml.dataset` functions into simple to use API. The main goals were:

* Focus on dataset manipulation functionality, leaving other parts of `tech.ml` like pipelines, datatypes, readers, ML, etc.
* Single entry point for common operations - one function dispatching on given arguments.
* `group-by` results with special kind of dataset - a dataset containing subsets created after grouping as a column.
* Most operations recognize regular dataset and grouped dataset and process data accordingly.
* One function form to enable thread-first on dataset.

Important! This library is not the replacement of `tech.ml.dataset` nor a separate library. It should be considered as a addition on the top of `tech.ml.dataset`.

If you want to know more about `tech.ml.dataset` and `dtype-next` please refer their documentation:

* [tech.ml.dataset walkthrough](https://techascent.github.io/tech.ml.dataset/walkthrough.html)
* [dtype-next overview](https://cnuernber.github.io/dtype-next/overview.html)
* [dtype-next cheatsheet](https://cnuernber.github.io/dtype-next/cheatsheet.html)

Join the discussion on [Zulip](https://clojurians.zulipchat.com/#narrow/stream/236259-tech.2Eml.2Edataset.2Edev/topic/api)

## Documentation

Please refer [detailed documentation with examples](https://scicloj.github.io/tablecloth/index.html)

## Usage example

```{clojure results="hide"}
(require '[tablecloth.api :as tc])
```

```{clojure results="asis"}
(-> "https://raw.githubusercontent.com/techascent/tech.ml.dataset/master/test/data/stocks.csv"
    (tc/dataset {:key-fn keyword})
    (tc/group-by (fn [row]
                    {:symbol (:symbol row)
                     :year (tech.v3.datatype.datetime/long-temporal-field :years (:date row))}))
    (tc/aggregate #(tech.v3.datatype.functional/mean (% :price)))
    (tc/order-by [:symbol :year])
    (tc/head 10))
```

## Contributing

`Tablecloth` is open for contribution. The best way to start is discussion on [Zulip](https://clojurians.zulipchat.com/#narrow/stream/236259-tech.2Eml.2Edataset.2Edev/topic/api).

### Development tools for documentation

Documentation is written in RMarkdown, that means that you need R to create html/md/pdf files. 
Documentation contains around 600 code snippets which are run during build. There are two files:

* `README.Rmd`
* `docs/index.Rmd`

Prepare following software:

1. Install [R](https://www.r-project.org/)
2. Install [rep](https://github.com/eraserhd/rep), nRepl client
3. Install `pandoc`
4. Run nRepl
5. Run R and install R packages: `install.packages(c("rmarkdown","knitr"), dependencies=T)`
6. Load rmarkdown: `library(rmarkdown)`
7. Render readme: `render("README.Rmd","md_document")`
8. Render documentation: `render("docs/index.Rmd","all")`

### API file generation

`tablecloth.api` namespace is generated out of `api-template`, please run it before making documentation

```{clojure eval=FALSE}
(exporter/write-api! 'tablecloth.api.api-template
                     'tablecloth.api
                     "src/tablecloth/api.clj"
                     '[group-by drop concat rand-nth first last shuffle])
```

### Guideline

1. Before commiting changes please perform tests. I ususally do: `lein do clean, check, test` and build documentation as described above (which also tests whole library).
2. Keep API as simple as possible:
    - first argument should be a dataset
    - if parametrizations is complex, last argument should accept a map with not obligatory function arguments
    - avoid variadic associative destructuring for function arguments
    - usually function should working on grouped dataset as well, accept `parallel?` argument then (if applied).
3. Follow `potemkin` pattern and import functions to the API namespace using `tech.v3.datatype.export-symbols/export-symbols` function
4. Functions which are composed out of API function to cover specific case(s) should go to `tablecloth.utils` namespace.
5. Always update `README.Rmd`, `CHANGELOG.md`, `docs/index.Rmd`, tests and function docs are highly welcomed
6. Always discuss changes and PRs first

## TODO

* tests
* tutorials

## New experimental dev workflow

In this branch, we develop a new proposed dev workflow for Tablecloth:
- namespace-as-a-notebook documentation using [Kindly](https://scicloj.github.io/kindly) and [Clay](https://scicloj.github.io/clay)
- testing the documentation using [note-to-test](https://github.com/scicloj/note-to-test) - coming soon

### Relevant files
- [notebooks/draft.clj](notebooks/draft.clj) - the tutorial as a Kindly notebook (developed with Clay)
  - [dev/conversion.clj](dev/conversion.clj) - the script used to generate the notebook from the original `Rmarkdown` tutorial (up to a few additional manual edits)
- [docs/draft.html](docs/draft.html) - the tutorial rendered using Clay and [Quarto](https://quarto.org/)

### Actions
- to render the notebook using Clay (assuming you have the Quarto CLI [installed](https://quarto.org/docs/get-started/)):
```clj
(require '[scicloj.clay.v2.api :as clay])
(clay/make! {:format [:quarto :html]
             :source-path "notebooks/draft.clj"})
```

## Licence

Copyright (c) 2020 Scicloj

The MIT Licence
