Filter dataframe on the fly-CodePudding

If we have to filter a dataframe we use the following based on variable name and its values

library(dplyr)
mtcars %>% filter(gear == 3)
# or
mtcars %>% filter(gear == 3 & carb == 3)
# or 
mtcars %>% filter(gear == 3 & carb == 3 & cyl == 8)

Instead of updating the code repeatedly What I want is dynamically filter the dataframes on the fly. Something like below

choice <-  c(gear == 3 & carb == 3 & cyl == 8)
mtcars %>% filter(choice)

I can select whatever variables I want to filter in the beginning and assign it to a variable and then simply pass that variable to filter function

The analogy to it is the following which is doing group by

choice <- c("gear", "carb", "cyl")
mtcars %>%
  group_by_at(vars(one_of(choice))) %>%
  summarize(Average=mean(mpg))

Is it doable in R?

CodePudding user response：

You may use an expression and evaluate it.

choice <- expression(gear == 3 & carb == 3 & cyl == 8)

mtcars |> subset(eval(choice))
#              mpg cyl  disp  hp drat   wt qsec vs am gear carb
# Merc 450SE  16.4   8 275.8 180 3.07 4.07 17.4  0  0    3    3
# Merc 450SL  17.3   8 275.8 180 3.07 3.73 17.6  0  0    3    3
# Merc 450SLC 15.2   8 275.8 180 3.07 3.78 18.0  0  0    3    3

Also works with dplyr.

library(magrittr)
mtcars %>% dplyr::filter(eval(choice))
#              mpg cyl  disp  hp drat   wt qsec vs am gear carb
# Merc 450SE  16.4   8 275.8 180 3.07 4.07 17.4  0  0    3    3
# Merc 450SL  17.3   8 275.8 180 3.07 3.73 17.6  0  0    3    3
# Merc 450SLC 15.2   8 275.8 180 3.07 3.78 18.0  0  0    3    3