An implementation of common higher order functions with syntactic sugar for anonymous function. Provides also a link to 'dplyr' and 'data.table' for common transformations on data frames to work around non standard evaluation by default.

Installation

From GitHub

remotes::install_github("wahani/dat")

From CRAN

install.packages("dat")

Why should you care?

Tools for data manipulation

The examples are from the introductory vignette of dplyr. You still work with data frames: so you can simply mix in dplyr features whenever you need them.

library("nycflights13")
library("dat")
## To use dplyr as backend set 'options(dat.use.dplyr = TRUE)'.
## 
## Attaching package: 'dat'
## The following object is masked from 'package:base':
## 
##     replace

Select rows

We can use mutar to select rows. When you reference a variable in the data frame, you can indicate this by using a one sided formula.

mutar(flights, ~ month == 1 & day == 1)
mutar(flights, ~ 1:10)

And for sorting:

mutar(flights, ~ order(year, month, day))
## # A tibble: 336,776 x 19
##     year month   day dep_time sched_dep_time dep_delay arr_time sched_arr_time
##    <int> <int> <int>    <int>          <int>     <dbl>    <int>          <int>
##  1  2013     1     1      517            515         2      830            819
##  2  2013     1     1      533            529         4      850            830
##  3  2013     1     1      542            540         2      923            850
##  4  2013     1     1      544            545        -1     1004           1022
##  5  2013     1     1      554            600        -6      812            837
##  6  2013     1     1      554            558        -4      740            728
##  7  2013     1     1      555            600        -5      913            854
##  8  2013     1     1      557            600        -3      709            723
##  9  2013     1     1      557            600        -3      838            846
## 10  2013     1     1      558            600        -2      753            745
## # … with 336,766 more rows, and 11 more variables: arr_delay <dbl>,
## #   carrier <chr>, flight <int>, tailnum <chr>, origin <chr>, dest <chr>,
## #   air_time <dbl>, distance <dbl>, hour <dbl>, minute <dbl>, time_hour <dttm>

Select cols

You can use characters, logicals, regular expressions and functions to select columns. Regular expressions are indicated by a leading “”.

flights %>%
  extract(c("year", "month", "day")) %>%
  extract("^day$") %>%
  extract(is.numeric)

Operations on columns

The main difference between dplyr::mutate and mutar is that you use a ~ instead of =.

mutar(
  flights,
  gain ~ arr_delay - dep_delay,
  speed ~ distance / air_time * 60
)

Grouping data is handled within mutar:

mutar(flights, n ~ .N, by = "month")
mutar(flights, delay ~ mean(dep_delay, na.rm = TRUE), by = "month")

You can also provide additional arguments to a formula. This is especially helpful when you want to pass arguments from a function to such expressions. The additional augmentation can be anything which you can use to select columns (character, regular expression, function) or a named list where each element is a character.

mutar(
  flights,
  .n ~ mean(.n, na.rm = TRUE) | "^.*delay$",
  .x ~ mean(.x, na.rm = TRUE) | list(.x = "arr_time"),
  by = "month"
)
## # A tibble: 336,776 x 19
##     year month   day dep_time sched_dep_time sched_arr_time carrier flight
##    <int> <int> <int>    <int>          <int>          <int> <chr>    <int>
##  1  2013     1     1      517            515            819 UA        1545
##  2  2013     1     1      533            529            830 UA        1714
##  3  2013     1     1      542            540            850 AA        1141
##  4  2013     1     1      544            545           1022 B6         725
##  5  2013     1     1      554            600            837 DL         461
##  6  2013     1     1      554            558            728 UA        1696
##  7  2013     1     1      555            600            854 B6         507
##  8  2013     1     1      557            600            723 EV        5708
##  9  2013     1     1      557            600            846 B6          79
## 10  2013     1     1      558            600            745 AA         301
## # … with 336,766 more rows, and 11 more variables: tailnum <chr>, origin <chr>,
## #   dest <chr>, air_time <dbl>, distance <dbl>, hour <dbl>, minute <dbl>,
## #   time_hour <dttm>, dep_delay <dbl>, arr_delay <dbl>, arr_time <dbl>

A link to S4

Using this package you can create S4 classes to contain a data frame (or a data.table) and use the interface to dplyr. Both dplyr and data.table do not support integration with S4. The main function here is mutar which is generic enough to link to subsetting of rows and cols as well as mutate and summarise. In the background dplyrs ability to work on a data.table is being used.

library("data.table")

setClass("DataTable", "data.table")

DataTable <- function(...) {
  new("DataTable", data.table::data.table(...))
}

setMethod("[", "DataTable", mutar)

dtflights <- do.call(DataTable, nycflights13::flights)

dtflights[1:10, c("year", "month", "day")]
dtflights[n ~ .N, by = "month"]
dtflights[n ~ .N, sby = "month"]

dtflights %>%
  filtar(~month > 6) %>%
  mutar(n ~ .N, by = "month") %>%
  sumar(n ~ data.table::first(n), by = "month")

Working with vectors

Inspired by rlist and purrr some low level operations on vectors are supported. The aim here is to integrate syntactic sugar for anonymous functions. Furthermore the functions should support the use of pipes.

What we can do with map:

map(1:3, ~ .^2)
flatmap(1:3, ~ .^2)
map(1:3 ~ 11:13, c) # zip
dat <- data.frame(x = 1, y = "")
map(dat, x ~ x + 1, is.numeric)

What we can do with extract:

extract(1:10, ~ . %% 2 == 0) %>% sum
extract(1:15, ~ 15 %% . == 0)
l <- list(aList = list(x = 1), aAtomic = "hi")
extract(l, "^aL")
extract(l, is.atomic)

What we can do with replace:

replace(c(1, 2, NA), is.na, 0)
replace(c(1, 2, NA), rep(TRUE, 3), 0)
replace(c(1, 2, NA), 3, 0)
replace(list(x = 1, y = 2), "x", 0)
replace(list(x = 1, y = 2), "^x$", 0)
replace(list(x = 1, y = "a"), is.character, NULL)