Suppose I have the following function
SlowFunction = function(vector){
return(list(
mean =mean(vector),
sd = sd(vector)
))
}
And I would like to use dplyr:summarise to write the results to a dataframe:
iris %>%
dplyr::group_by(Species) %>%
dplyr::summarise(
mean = SlowFunction(Sepal.Length)$mean,
sd = SlowFunction(Sepal.Length)$sd
)
Does anyone have a suggestion how I can do this by calling "SlowFunction" once instead of twice? (In my code "SlowFunction" is a slow function that I have to call many times.) Without splitting "SlowFunction" in two parts of course. So actually I would like to somehow fill multiple columns of a dataframe in one statement.
Without changing your current SlowFunction one way is to use do
library(dplyr)
iris %>%
group_by(Species) %>%
do(data.frame(SlowFunction(.$Sepal.Length)))
# Species mean sd
# <fct> <dbl> <dbl>
#1 setosa 5.01 0.352
#2 versicolor 5.94 0.516
#3 virginica 6.59 0.636
Or with group_split + purrr::map_dfr
bind_cols(Species = unique(iris$Species), iris %>%
group_split(Species) %>%
map_dfr(~SlowFunction(.$Sepal.Length)))
An option is to use to store the output of SlowFunction in a list column of data.frames and then to use unnest
iris %>%
group_by(Species) %>%
summarise(res = list(as.data.frame(SlowFunction(Sepal.Length)))) %>%
unnest()
## A tibble: 3 x 3
# Species mean sd
# <fct> <dbl> <dbl>
#1 setosa 5.01 0.352
#2 versicolor 5.94 0.516
#3 virginica 6.59 0.636
We can use group_map if you are using dplyr 0.8.0 or later. The output from SlowFunction needs to be converted to a data frame.
library(dplyr)
iris %>%
group_by(Species) %>%
group_map(~SlowFunction(.x$Sepal.Length) %>% as.data.frame())
# # A tibble: 3 x 3
# # Groups: Species [3]
# Species mean sd
# <fct> <dbl> <dbl>
# 1 setosa 5.01 0.352
# 2 versicolor 5.94 0.516
# 3 virginica 6.59 0.636
We can change the SlowFunction to return a tibble and
SlowFunction = function(vector){
tibble(
mean =mean(vector),
sd = sd(vector)
)
}
and then unnest the summarise output in a list
iris %>%
group_by(Species) %>%
summarise(out = list(SlowFunction(Sepal.Length))) %>%
unnest
# A tibble: 3 x 3
# Species mean sd
# <fct> <dbl> <dbl>
#1 setosa 5.01 0.352
#2 versicolor 5.94 0.516
#3 virginica 6.59 0.636
Related
I'd like to group multiple t test result into one table. Originally my code looks like this:
tt_data <- iris %>%
group_by(Species) %>%
summarise(p = t.test(Sepal.Length,Petal.Length,alternative="two.sided",paired=T)$p.value,
estimate = t.test(Sepal.Length,Petal.Length,alternative="two.sided",paired=T)$estimate
)
tt_data
# Species p estimate
# setosa 2.542887e-51 3.544
# versicolor 9.667914e-36 1.676
# virginica 7.985259e-28 1.036
However, base on the idea that I should only perform the statistical test once, is there a way for me to run t test once per group and collect the intended table? I think there are some combination of broom and purrr but I am unfamiliar with the syntax.
# code idea (I know this won't work!)
tt_data <- iris %>%
group_by(Species) %>%
summarise(tt = t.test(Sepal.Length,Petal.Length,alternative="two.sided",paired=T)) %>%
select(Species, tt.p, tt.estimate)
tt_data
# Species tt.p tt.estimate
# setosa 2.542887e-51 3.544
# versicolor 9.667914e-36 1.676
# virginica 7.985259e-28 1.036
You can use broom::tidy() to transform the resut of the t.test to a tidy 'tibble':
library(dplyr)
library(broom)
iris %>%
group_by(Species) %>%
group_modify(~{
t.test(.$Sepal.Length,.$Petal.Length,alternative="two.sided",paired=T) %>%
tidy()
}) %>%
select(estimate, p.value)
#> Adding missing grouping variables: `Species`
#> # A tibble: 3 x 3
#> # Groups: Species [3]
#> Species estimate p.value
#> <fct> <dbl> <dbl>
#> 1 setosa 3.54 2.54e-51
#> 2 versicolor 1.68 9.67e-36
#> 3 virginica 1.04 7.99e-28
Created on 2020-09-02 by the reprex package (v0.3.0)
You can use map to select the desired values from the list generated by t.test and by tidying it up to a data frame via broom::tidy, i.e.
library(dplyr)
iris %>%
group_by(Species) %>%
summarise(p = list(broom::tidy(t.test(Sepal.Length, Petal.Length, alternative = "two.sided", paired = T)))) %>%
mutate(p.value = purrr::map(p, ~select(.x, c('p.value', 'estimate')))) %>%
select(-p) %>%
unnest()
# A tibble: 3 x 3
# Species p.value estimate
# <fct> <dbl> <dbl>
#1 setosa 2.54e-51 3.54
#2 versicolor 9.67e-36 1.68
#3 virginica 7.99e-28 1.04
Suppose we want to group_by() and summarise a massive data.frame with very many columns, but that there are some large groups of consecutive columns that will have the same summarise condition (e.g. max, mean etc)
Is there a way to avoid having to specify the summarise condition for each and every column, and instead do it for ranges of columns?
Example
Suppose we want to do this:
iris %>%
group_by(Species) %>%
summarise(max(Sepal.Length), mean(Sepal.Width), mean(Petal.Length), mean(Petal.Width))
but note that 3 consecutive columns have the same summarise condition, mean(Sepal.Width), mean(Petal.Length), mean(Petal.Width)
Is there a way to use some method like mean(Sepal.Width:Petal.Width) to specify the condition for the range of columns, and hence a avoiding having to type out the summarise condition multiple times for all the columns in between)
Note
The iris example above is a small and manageable example that has a range of 3 consecutive columns, but actual use case has ~hundreds.
The upcoming version 1.0.0 of dplyr will have across() function that does what you wish for
Basic usage
across() has two primary arguments:
The first argument, .cols, selects the columns you want to operate on.
It uses tidy selection (like select()) so you can pick variables by
position, name, and type.
The second argument, .fns, is a function or list of functions to apply to
each column. This can also be a purrr style formula (or list of formulas)
like ~ .x / 2. (This argument is optional, and you can omit it if you just want
to get the underlying data; you'll see that technique used in
vignette("rowwise").)
### Install development version on GitHub first
# install.packages("devtools")
# devtools::install_github("tidyverse/dplyr")
library(dplyr, warn.conflicts = FALSE)
Control how the names are created with the .names argument which takes a glue spec:
iris %>%
group_by(Species) %>%
summarise(
across(c(Sepal.Width:Petal.Width), ~ mean(.x, na.rm = TRUE), .names = "mean_{col}"),
across(c(Sepal.Length), ~ max(.x, na.rm = TRUE), .names = "max_{col}")
)
#> # A tibble: 3 x 5
#> Species mean_Sepal.Width mean_Petal.Leng~ mean_Petal.Width max_Sepal.Length
#> * <fct> <dbl> <dbl> <dbl> <dbl>
#> 1 setosa 3.43 1.46 0.246 5.8
#> 2 versicolor 2.77 4.26 1.33 7
#> 3 virginica 2.97 5.55 2.03 7.9
Using multiple functions
my_func <- list(
mean = ~ mean(., na.rm = TRUE),
max = ~ max(., na.rm = TRUE)
)
iris %>%
group_by(Species) %>%
summarise(across(where(is.numeric), my_func, .names = "{fn}.{col}"))
#> # A tibble: 3 x 9
#> Species mean.Sepal.Length max.Sepal.Length mean.Sepal.Width max.Sepal.Width
#> * <fct> <dbl> <dbl> <dbl> <dbl>
#> 1 setosa 5.01 5.8 3.43 4.4
#> 2 versicolor 5.94 7 2.77 3.4
#> 3 virginica 6.59 7.9 2.97 3.8
#> mean.Petal.Length max.Petal.Length mean.Petal.Width max.Petal.Width
#> * <dbl> <dbl> <dbl> <dbl>
#> 1 1.46 1.9 0.246 0.6
#> 2 4.26 5.1 1.33 1.8
#> 3 5.55 6.9 2.03 2.5
Created on 2020-03-06 by the reprex package (v0.3.0)
Since summarise collapses the rows and hence we cannot further apply any functions to it, we can use mutate_at instead, select range of columns to apply function and then select 1st row from every group.
library(dplyr)
iris %>%
group_by(Species) %>%
mutate_at(vars(Sepal.Width:Petal.Width), mean) %>%
mutate_at(vars(Sepal.Length), max) %>%
slice(1L)
# Sepal.Length Sepal.Width Petal.Length Petal.Width Species
# <dbl> <dbl> <dbl> <dbl> <fct>
#1 5.8 3.43 1.46 0.246 setosa
#2 7 2.77 4.26 1.33 versicolor
#3 7.9 2.97 5.55 2.03 virginica
We can use pmap from purrr to apply various functions to various columns and then join back together at the end. Note the use of lst from purrr so we can refer to previously named objects in the list construction. This allows us to analyze the same column with multiple functions, such as Sepal.Length below.
library(tidyverse)
lst(a = list("Sepal.Length", names(select(iris, Sepal.Length:Petal.Width))),
b = list("max" = max, "mean" = mean),
c = names(b)) %>%
pmap(function(a, b, c) {
iris %>%
group_by(Species) %>%
summarize_at(a, b) %>%
rename_at(a, paste0, "_", c)
}) %>%
reduce(inner_join, by = "Species")
#> # A tibble: 3 x 6
#> Species Sepal.Length_max Sepal.Length_me~ Sepal.Width_mean Petal.Length_me~
#> <fct> <dbl> <dbl> <dbl> <dbl>
#> 1 setosa 5.8 5.01 3.43 1.46
#> 2 versic~ 7 5.94 2.77 4.26
#> 3 virgin~ 7.9 6.59 2.97 5.55
#> # ... with 1 more variable: Petal.Width_mean <dbl>
I'm creating a bunch of basic status reports and one of things I'm finding tedious is adding a total row to all my tables. I'm currently using the Tidyverse approach and this is an example of my current code. What I'm looking for is an option to have a few different levels included by default.
#load into RStudio viewer (not required)
iris = iris
#summary at the group level
summary_grouped = iris %>%
group_by(Species) %>%
summarize(mean_s_length = mean(Sepal.Length),
max_s_width = max(Sepal.Width))
#summary at the overall level
summary_overall = iris %>%
summarize(mean_s_length = mean(Sepal.Length),
max_s_width = max(Sepal.Width)) %>%
mutate(Species = "Overall")
#append results for report
summary_table = rbind(summary_grouped, summary_overall)
Doing this multiple times over is very tedious. I kind of want:
summary_overall = iris %>%
group_by(Species, total = TRUE) %>%
summarize(mean_s_length = mean(Sepal.Length),
max_s_width = max(Sepal.Width))
FYI - if you're familiar with SAS I'm looking for the same type of functionality available via a class, ways or types statements in proc means that let me control the level of summarization and get multiple levels in one call.
Any help is appreciated. I know I can create my own function, but was hoping there is something that already exists. I would also prefer to stick with the tidyverse style of programming though I'm not set on that.
Another alternative:
library(tidyverse)
iris %>%
mutate_at("Species", as.character) %>%
list(group_by(.,Species), .) %>%
map(~summarize(.,mean_s_length = mean(Sepal.Length),
max_s_width = max(Sepal.Width))) %>%
bind_rows() %>%
replace_na(list(Species="Overall"))
#> # A tibble: 4 x 3
#> Species mean_s_length max_s_width
#> <chr> <dbl> <dbl>
#> 1 setosa 5.01 4.4
#> 2 versicolor 5.94 3.4
#> 3 virginica 6.59 3.8
#> 4 Overall 5.84 4.4
You can write a function which does the same summarize on an ungrouped tibble and rbinds that to the end.
summarize2 <- function(df, ...){
bind_rows(summarise(df, ...), summarize(ungroup(df), ...))
}
iris %>%
group_by(Species) %>%
summarize2(
mean_s_length = mean(Sepal.Length),
max_s_width = max(Sepal.Width)
)
# # A tibble: 4 x 3
# Species mean_s_length max_s_width
# <fct> <dbl> <dbl>
# 1 setosa 5.01 4.4
# 2 versicolor 5.94 3.4
# 3 virginica 6.59 3.8
# 4 NA 5.84 4.4
You could add some logic for what the "Overall" groups should be named if you want
summarize2 <- function(df, ...){
s1 <- summarise(df, ...)
s2 <- summarize(ungroup(df), ...)
for(v in group_vars(s1)){
if(is.factor(s1[[v]]))
s1[[v]] <- as.character(s1[[v]])
if(is.character(s1[[v]]))
s2[[v]] <- 'Overall'
else if(is.numeric(s1[[v]]))
s2[[v]] <- -Inf
}
bind_rows(s1, s2)
}
iris %>%
group_by(Species, g = Petal.Length %/% 1) %>%
summarize2(
mean_s_length = mean(Sepal.Length),
max_s_width = max(Sepal.Width)
)
# # Groups: Species [4]
# Species g mean_s_length max_s_width
# <chr> <dbl> <dbl> <dbl>
# 1 setosa 1 5.01 4.4
# 2 versicolor 3 5.35 2.9
# 3 versicolor 4 6.09 3.4
# 4 versicolor 5 6.35 3
# 5 virginica 4 5.85 3
# 6 virginica 5 6.44 3.4
# 7 virginica 6 7.43 3.8
# 8 Overall -Inf 5.84 4.4
library(dplyr)
iris %>%
group_by(Species) %>%
summarize(mean_s_length = mean(Sepal.Length),
max_s_width = max(Sepal.Width)) %>%
ungroup() %>%
mutate_at(vars(Species), as.character) %>%
{rbind(.,c("Overal",mean(.$mean_s_length),max(.$max_s_width)))} %>%
mutate_at(vars(-Species), as.double) %>%
mutate_at(vars(Species), as.factor)
#> # A tibble: 4 x 3
#> Species mean_s_length max_s_width
#> <fct> <dbl> <dbl>
#> 1 setosa 5.01 4.4
#> 2 versicolor 5.94 3.4
#> 3 virginica 6.59 3.8
#> 4 Overal 5.84 4.4
Created on 2019-06-21 by the reprex package (v0.3.0)
One way, also tedious but in one longer pipe, is to put the second summarise instructions in bind_rows.
The as.character call avoids a warning:
Warning messages:
1: In bind_rows_(x, .id) :
binding factor and character vector, coercing into character vector
2: In bind_rows_(x, .id) :
binding character and factor vector, coercing into character vector
library(tidyverse)
summary_grouped <- iris %>%
mutate(Species = as.character(Species)) %>%
group_by(Species) %>%
summarize(mean_s_length = mean(Sepal.Length),
max_s_width = max(Sepal.Width)) %>%
bind_rows(iris %>%
summarize(mean_s_length = mean(Sepal.Length),
max_s_width = max(Sepal.Width)) %>%
mutate(Species = "Overall"))
## A tibble: 4 x 3
# Species mean_s_length max_s_width
# <chr> <dbl> <dbl>
#1 setosa 5.01 4.4
#2 versicolor 5.94 3.4
#3 virginica 6.59 3.8
#4 Overall 5.84 4.4
Maybe something like this:
As you want to perform different operations on the same input (iris), best to map over the different summary functions and apply to the data.
map_dfr combines the list outputs using bind_rows
library(dplyr)
library(purrr)
pipe <- . %>%
group_by(Species) %>%
summarize(
mean_s_length = mean(Sepal.Length),
max_s_width = max(Sepal.Width))
map_dfr(
list(pipe, . %>% mutate(Species = "Overall") %>% pipe),
exec,
iris)
#> Warning in bind_rows_(x, .id): binding factor and character vector,
#> coercing into character vector
#> Warning in bind_rows_(x, .id): binding character and factor vector,
#> coercing into character vector
#> # A tibble: 4 x 3
#> Species mean_s_length max_s_width
#> <chr> <dbl> <dbl>
#> 1 setosa 5.01 4.4
#> 2 versicolor 5.94 3.4
#> 3 virginica 6.59 3.8
#> 4 Overall 5.84 4.4
Solution where you need to apply wanted function only once on a double dataset:
library(tidyverse)
iris %>%
rbind(mutate(., Species = "Overall")) %>%
group_by(Species) %>%
summarize(
mean_s_length = mean(Sepal.Length),
max_s_width = max(Sepal.Width)
)
# A tibble: 4 x 3
Species mean_s_length max_s_width
<chr> <dbl> <dbl>
1 Overall 5.84 4.4
2 setosa 5.01 4.4
3 versicolor 5.94 3.4
4 virginica 6.59 3.8
Trick is to pass original dataset with a new group ID (ie Species): mutate(iris, Species = "Overall")
I would like to pre-assign my column name and use that within a dplyr pipe
Here's an example. I want to do this:
iris %>%
group_by(Species) %>%
summarise(Var = mean(Petal.Length[Sepal.Width > 3]))
But with the column name assigned outside of the pipe, like this
col_name <- "Petal.Length"
iris %>%
group_by(Species) %>%
summarise(Var = mean(!!col_name[Sepal.Width > 3]))
We can convert to symbol (sym) and then do the evaluation (!!)
iris %>%
group_by(Species) %>%
summarise(Var = mean((!!rlang::sym(col_name))[Sepal.Width >3]))
# A tibble: 3 x 2
# Species Var
# <fct> <dbl>
#1 setosa 1.48
#2 versicolor 4.65
#3 virginica 5.72
If we need to use only dplyr, then can pass the variable object in summarise_at
iris %>%
group_by(Species) %>%
summarise_at(vars(col_name), funs(mean(.[Sepal.Width > 3])))
# A tibble: 3 x 2
# Species Petal.Length
# <fct> <dbl>
#1 setosa 1.48
#2 versicolor 4.65
#3 virginica 5.72
I would like to use summarise() from dplyr after grouping data to compute a new variable. But, I would like it to use one equation for some of the data and a second equation for the rest of the data.
I have tried using group_by() and and summarise() with if_else() but it isn't working.
Here's an example. Let's say--for some reason--I wanted to find a special value for sepal length. For the species 'setosa' this special value is twice the mean of the sepal length. For all of the other species it is simply the mean of sepal length. This is the code I've tried, but it doesn't work with summarise()
library(dplyr)
iris %>%
group_by(Species) %>%
summarise(sepal_special = if_else(Species == "setosa", mean(Sepal.Length)*2, mean(Sepal.Length)))
This idea works with mutate() but I would need to re-format the tibble to be the dataset I am looking for.
library(dplyr)
iris %>%
group_by(Species) %>%
mutate(sepal_special = if_else(Species == "setosa", mean(Sepal.Length)*2, mean(Sepal.Length)))
This is how I want the resulting tibble to be laid out:
library(dplyr)
iris %>%
group_by(Species)%>%
summarise(sepal_mean = mean(Sepal.Length))
# A tibble: 3 x 2
# Species sepal_special
# <fctr> <dbl>
#1 setosa 5.01
#2 versicolor 5.94
#3 virginica 6.59
#>
But my result would show the value for setosa x 2
# A tibble: 3 x 2
# Species sepal_special
# <fctr> <dbl>
#1 setosa **10.02**
#2 versicolor 5.94
#3 virginica 6.59
#>
Suggestions? I feel like I've really searched for ways to use if_else() with summarise() but can't find it anywhere, which means there must be a better way.
Thanks!
After the mutate step, use summarise to get the first element of 'sepal_special' for each 'Species'
iris %>%
group_by(Species) %>%
mutate(sepal_special = if_else(Species == "setosa",
mean(Sepal.Length)*2, mean(Sepal.Length))) %>%
summarise(sepal_special = first(sepal_special))
# A tibble: 3 x 2
# Species sepal_special
# <fctr> <dbl>
#1 setosa 10.0
#2 versicolor 5.94
#3 virginica 6.59
Or instead of calling the mutate, after the if_else is applied, get the first value in summarise
iris %>%
group_by(Species) %>%
summarise(sepal_special = if_else(Species == "setosa",
mean(Sepal.Length)*2, mean(Sepal.Length))[1])
# A tibble: 3 x 2
# Species sepal_special
# <fctr> <dbl>
#1 setosa 10.0
#2 versicolor 5.94
#3 virginica 6.59
Another option: since twice the mean is the same as the mean of twice the values, you can double the sepal lengths for setosa and then summarise:
iris %>%
mutate(Sepal.Length = ifelse(Species == "setosa", 2*Sepal.Length, Sepal.Length)) %>%
group_by(Species) %>%
summarise(sepal_special = mean(Sepal.Length))
# A tibble: 3 x 2
Species sepal_special
<fct> <dbl>
1 setosa 10.0
2 versicolor 5.94
3 virginica 6.59