Can Dplyr Summarise Over Several Variables Without Listing Each One

Can dplyr summarise over several variables without listing each one?

The data.table idiom is lapply(.SD, mean), which is

DT <- data.table(df)
DT[, lapply(.SD, mean), by = sex]
#     sex age bmi  chol
# 1:  boy  55  24 203.5
# 2: girl  51  28 197.0

I'm not sure of a dplyr idiom for the same thing, but you can do something like

dg <- group_by(df, sex)
# the names of the columns you want to summarize
cols <- names(dg)[-1]
# the dots component of your call to summarise
dots <- sapply(cols ,function(x) substitute(mean(x), list(x=as.name(x))))
do.call(summarise, c(list(.data=dg), dots))
# Source: local data frame [2 x 4]

#    sex age bmi  chol
# 1  boy  55  24 203.5
# 2 girl  51  28 197.0

Note that there is a github issue #178 to efficienctly implement the plyr idiom colwise in dplyr.

Summarizing multiple columns with dplyr?

In dplyr (>=1.00) you may use across(everything() in summarise to apply a function to all variables:

library(dplyr)

df %>% group_by(grp) %>% summarise(across(everything(), list(mean)))
#> # A tibble: 3 x 5
#>     grp     a     b     c     d
#>   <int> <dbl> <dbl> <dbl> <dbl>
#> 1     1  3.08  2.98  2.98  2.91
#> 2     2  3.03  3.04  2.97  2.87
#> 3     3  2.85  2.95  2.95  3.06

Alternatively, the purrrlyr package provides the same functionality:

library(purrrlyr)
df %>% slice_rows("grp") %>% dmap(mean)
#> # A tibble: 3 x 5
#>     grp     a     b     c     d
#>   <int> <dbl> <dbl> <dbl> <dbl>
#> 1     1  3.08  2.98  2.98  2.91
#> 2     2  3.03  3.04  2.97  2.87
#> 3     3  2.85  2.95  2.95  3.06

Also don't forget about data.table (use keyby to sort sort groups):

library(data.table)
setDT(df)[, lapply(.SD, mean), keyby = grp]
#>    grp        a        b        c        d
#> 1:   1 3.079412 2.979412 2.979412 2.914706
#> 2:   2 3.029126 3.038835 2.967638 2.873786
#> 3:   3 2.854701 2.948718 2.951567 3.062678

Let's try to compare performance.

library(dplyr)
library(purrrlyr)
library(data.table)
library(bench)
set.seed(123)
n <- 10000
df <- data.frame(
  a = sample(1:5, n, replace = TRUE), 
  b = sample(1:5, n, replace = TRUE), 
  c = sample(1:5, n, replace = TRUE), 
  d = sample(1:5, n, replace = TRUE), 
  grp = sample(1:3, n, replace = TRUE)
)
dt <- setDT(df)
mark(
  dplyr = df %>% group_by(grp) %>% summarise(across(everything(), list(mean))),
  purrrlyr = df %>% slice_rows("grp") %>% dmap(mean),
  data.table = dt[, lapply(.SD, mean), keyby = grp],
  check = FALSE
)
#> # A tibble: 3 x 6
#>   expression      min   median `itr/sec` mem_alloc `gc/sec`
#>   <bch:expr> <bch:tm> <bch:tm>     <dbl> <bch:byt>    <dbl>
#> 1 dplyr        2.81ms   2.85ms      328.        NA     17.3
#> 2 purrrlyr     7.96ms   8.04ms      123.        NA     24.5
#> 3 data.table 596.33µs 707.91µs     1409.        NA     10.3

When using `dplyr::summarise()` with the `across()` function can I mix the list and formula syntax

To apply multiple functions in the same across statement you can use the list syntax as :

library(dplyr)

iris %>%
  group_by(Species) %>%
  summarise(across(starts_with("Sepal"), list(sum = ~sum(!is.na(.)), 
                                              mean = mean, sd = sd)))

dplyr summarise : Group by multiple variables in a loop and add results in the same dataframe

library(questionr)
library(tidyverse)
data(hdv2003)

list("trav.satisf", "cuisine", "sexe") %>%
  map(~ {
    hdv2003 %>%
      group_by_at(.x) %>%
      summarise(
        n = n(),
        percent = round((n() / nrow(hdv2003)) * 100, digits = 1),
        femmes = round((sum(sexe == "Femme", na.rm = TRUE) / sum(!is.na(sexe))) * 100, digits = 1),
        age = round(mean(age, na.rm = TRUE), digits = 1)
      ) %>%
      rename_at(1, ~"group") %>%
      mutate(grouping = .x)
  }) %>%
  bind_rows() %>%
  select(grouping, group, everything())
#> # A tibble: 8 x 6
#>   grouping    group              n percent femmes   age
#>   <chr>       <fct>          <int>   <dbl>  <dbl> <dbl>
#> 1 trav.satisf Satisfaction     480    24     51.5  41.4
#> 2 trav.satisf Insatisfaction   117     5.9   47.9  40.3
#> 3 trav.satisf Equilibre        451    22.6   49.9  40.9
#> 4 trav.satisf <NA>             952    47.6   60.2  56  
#> 5 cuisine     Non             1119    56     43.8  50.1
#> 6 cuisine     Oui              881    44     69.4  45.6
#> 7 sexe        Homme            899    45      0    48.2
#> 8 sexe        Femme           1101    55    100    48.2

^{Created on 2021-11-12 by the reprex package (v2.0.1)}

dplyr: add new variables in summarise for each variable name in a vector

There is a summarise_at just for this:

iris
  %>% group_by(Species)
  %>% summarise_at(c("Sepal.Length", "Sepal.Width"), funs(mean, sd), na.rm=TRUE)

# A tibble: 3 x 5
  Species    Sepal.Length_mean Sepal.Width_mean Sepal.Length_sd Sepal.Width_sd
  <fct>                  <dbl>            <dbl>           <dbl>          <dbl>
1 setosa                  5.01             3.43           0.352          0.379
2 versicolor              5.94             2.77           0.516          0.314
3 virginica               6.59             2.97           0.636          0.322

Summarise multiple columns that have to be grouped tidyverse

Get the data in long format and count :

library(dplyr)
library(tidyr)

df %>% pivot_longer(cols = one:three) %>% count(group1, group2, value)

#  group1 group2 value     n
#  <chr>  <chr>  <chr> <int>
#1 High   female no        1
#2 High   female yes       2
#3 High   male   no        3
#4 High   male   yes       3
#5 Low    female no        2
#6 Low    female yes       4
#7 Low    male   no        1
#8 Low    male   yes       2

Using dplyr summarize with different operations for multiple columns

As other people have mentioned, this is normally done by calling summarize_each / summarize_at / summarize_if for every group of columns that you want to apply the summarizing function to. As far as I know, you would have to create a custom function that performs summarizations to each subset. You can for example set the colnames in such way that you can use the select helpers (e.g. contains()) to filter just the columns that you want to apply the function to. If not, then you can set the specific column numbers that you want to summarize.

For the example you mentioned, you could try the following:

summarizer <- function(tb, colsone, colstwo, colsthree, 
                       funsone, funstwo, funsthree, group_name) {

return(bind_cols(
    summarize_all(select(tb, colsone), .funs = funsone),
    summarize_all(select(tb, colstwo), .funs = funstwo) %>% 
      ungroup() %>% select(-matches(group_name)),
    summarize_all(select(tb, colsthree), .funs = funsthree) %>% 
      ungroup() %>% select(-matches(group_name)) 
))

}

#With colnames
iris %>% as.tibble() %>% 
  group_by(Species) %>% 
  summarizer(colsone = contains("Sepal"), 
         colstwo = matches("Petal.Length"), 
         colsthree = c(-contains("Sepal"), -matches("Petal.Length")),
         funsone = "sum", 
         funstwo = "mean",
         funsthree = "first",
         group_name = "Species")

#With indexes
iris %>% as.tibble() %>% 
 group_by(Species) %>% 
 summarizer(colsone = 1:2, 
         colstwo = 3, 
         colsthree = 4,
         funsone = "sum", 
         funstwo = "mean",
         funsthree = "first",
         group_name = "Species")

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