In hope-data-science/tidydt: Tidy Verbs for 'data.table'

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

When I design longer_dt and wider_dt, I could find the pivot_longer and pivot_wider in tidyr and melt and dcast in data.table. Still, designing this API is not easy, as my goal is to let users use it with least pain. Here we would try to reproduce the results in the vignette of tidyr(https://cran.r-project.org/web/packages/tidyr/vignettes/pivot.html). First load the packages:

library(tidydt)
library(tidyr)

Longer

First inspect the data:

relig_income

In tidyr, to get the longer format you need:

relig_income %>% 
  pivot_longer(-religion, names_to = "income", values_to = "count")

In tidydt, we have:

relig_income %>% 
  longer_dt(group_to_keep = "religion",gathered_name = "income",gathered_value = "count")

Another example from tidyr:

billboard

# tidyr way:
# billboard %>% 
#   pivot_longer(
#     cols = starts_with("wk"), 
#     names_to = "week", 
#     values_to = "rank",
#     values_drop_na = TRUE
#   )

# tidydt way:
billboard %>% 
  longer_dt("wk",negate = TRUE,  
            gathered_name = "week",
            gathered_value = "rank",
            na.rm = TRUE
            )
# regex should select group_to_keep, negate could reverse that

A warning would could come out because the merging column has different data types and do the coercion automatically.

Wider

## data
fish_encounters

## tidyr way:
fish_encounters %>% pivot_wider(names_from = station, values_from = seen)

## tidydt way:
fish_encounters %>% 
  wider_dt(name_to_spread = "station",value_to_spread = "seen")

If you want to fill with 0s, use:

fish_encounters %>% 
  wider_dt(name_to_spread = "station",value_to_spread = "seen",fill = 0)

tidydt currently does not support spreading multiple columns. I believe this way could keep this function simple and easy to understand. When you need this function, try spread them one by one (using a loop), or try data.table and tidyr.

hope-data-science/tidydt documentation built on Feb. 21, 2020, 10:25 a.m.