Nest and unnest
Create or melt list columns in data.frame.
Analogous function for nest and unnest in tidyr.
unnest_dt will automatically remove other list-columns except for the
target list-columns (which would be unnested later). Also, squeeze_dt is
designed to merge multiple columns into list column.
nest_dt(.data, ..., mcols = NULL, .name = "ndt") unnest_dt(.data, ...) squeeze_dt(.data, ..., .name = "ndt") chop_dt(.data, ...) unchop_dt(.data, ...)
.data |
data.table, nested or unnested |
... |
The variables for nest group(for |
mcols |
Name-variable pairs in the list, form like |
.name |
Character. The nested column name. Defaults to "ndt".
|
In the nest_dt, the data would be nested to a column named 'ndt',
which is short for nested data.table.
The squeeze_dt would not remove the originial columns.
The unchop_dt is the reverse operation of chop_dt.
These functions are experiencing the experimental stage, especially
the unnest_dt. If they don't work on some circumtances, try tidyr
package.
data.table, nested or unnested
https://www.r-bloggers.com/much-faster-unnesting-with-data-table/
https://stackoverflow.com/questions/25430986/create-nested-data-tables-by-collapsing-rows-into-new-data-tables
# examples for nest_dt
# nest by which columns?
mtcars %>% nest_dt(cyl)
mtcars %>% nest_dt("cyl")
mtcars %>% nest_dt(cyl,vs)
mtcars %>% nest_dt(vs:am)
mtcars %>% nest_dt("cyl|vs")
mtcars %>% nest_dt(c("cyl","vs"))
# change the nested column name
mtcars %>% nest_dt(cyl,.name = "data")
# nest two columns directly
iris %>% nest_dt(mcols = list(petal="^Pe",sepal="^Se"))
# nest more flexibly
iris %>% nest_dt(mcols = list(ndt1 = 1:3,
ndt2 = "Pe",
ndt3 = Sepal.Length:Sepal.Width))
# examples for unnest_dt
# unnest which column?
mtcars %>% nest_dt("cyl|vs") %>%
unnest_dt(ndt)
mtcars %>% nest_dt("cyl|vs") %>%
unnest_dt("ndt")
df <- data.table(
a = list(c("a", "b"), "c"),
b = list(c(TRUE,TRUE),FALSE),
c = list(3,c(1,2)),
d = c(11, 22)
)
df
df %>% unnest_dt(a)
df %>% unnest_dt(2)
df %>% unnest_dt("c")
df %>% unnest_dt(cols = names(df)[3])
# You can unnest multiple columns simultaneously
df %>% unnest_dt(1:3)
df %>% unnest_dt(a,b,c)
df %>% unnest_dt("a|b|c")
# examples for squeeze_dt
# nest which columns?
iris %>% squeeze_dt(1:2)
iris %>% squeeze_dt("Se")
iris %>% squeeze_dt(Sepal.Length:Petal.Width)
iris %>% squeeze_dt(1:2,.name = "data")
# examples for chop_dt
df <- data.table(x = c(1, 1, 1, 2, 2, 3), y = 1:6, z = 6:1)
df %>% chop_dt(y,z)
df %>% chop_dt(y,z) %>% unchop_dt(y,z)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.