README.md

tabular - SQL-like constraints for data frames

Purpose

This package is to add safety to poor man's data bases consisting of a collection of R data frames.

In a true, SQL-based relational data base, we can design the individual tables such that constrains apply to certain columns (or combinations of columns). The widely used constraints are

Such constraints are of vital importance for data integrity. Unfortunately, R has no built-in mechanism to impose those constrains on data frames and collections thereof. This package is to provides a pragmatic solution to this issue.

Example

In this example, we create a poor man's data base consisting of two join-able data frames. Well' then write a function to check the integrity of this data base. Wrapping all checks into a dedicated function is recommended since this function can be called repeatedly, e.g. after insert or delete operations.

library("tabular")

# test data
countries <- read.table(header=TRUE, text='
id name
1  USA
2  UK
3  Russia
')

bosses <- read.table(header=TRUE, text='
id name    id_country
1  Trump   1
2  Johnson 2
3  Blair   2
4  Putin   3
')

# validation function taking a list of data frames as argument
validate <- function(database) {
  with(database, {
    # primary key and unique constraints
    stopifnot(check.key(countries, "id"))
    stopifnot(check.unique(countries, "name"))
    stopifnot(check.notnull(countries, "name"))
    stopifnot(check.key(bosses, "id"))
    stopifnot(check.unique(bosses, "name"))
    stopifnot(check.notnull(bosses, "name"))
    # foreign key constraint
    stopifnot(check.link(bosses, "id_country", countries, "id"))
  })
  invisible(NULL)
}

# application of the validation function
db <- list(countries=countries, bosses=bosses)
validate(db)

Requirements and installation

The development version of the package can be installed from github as shown below. A CRAN version may become available later once the package has matured.

# Install and load development version
library("devtools")
install_github("dkneis/tabular")
library("tabular")


dkneis/tabular documentation built on July 5, 2021, 4:12 a.m.