I have a problem!
I want to define a function to select variable of a df
like that
select_var <- function(var1, var2)
{
require(dplyr)
select(df=df,var1,var2)
}
using select_var like select_var(var_name_1,var_name_2)
without "".
I want to my df my variable !
Then I want to add var 3 var 4 but there are OPTIONNALS SETTING you!thank you !
You can use enquo and !! as in:
select_var <- function(var1, var2)
{
require(tidyverse)
var1 <- enquo(var1)
var2 <- enquo(var2)
select(mtcars, !!var1, !!var2)
}
select_var(mpg, gear)
# mpg gear
#Mazda RX4 21.0 4
#Mazda RX4 Wag 21.0 4
#Datsun 710 22.8 4
#Hornet 4 Drive 21.4 3
#Hornet Sportabout 18.7 3
#Valiant 18.1 3
# ...
Not sure what you mean by optionals, but maybe something like:
select_var <- function(...)
{
require(tidyverse)
vars <- quos(...)
select(mtcars, !!!vars)
}
select_var(mpg)
select_var(mpg, gear)
select_var(mpg, gear, cyl)
You can select rows from the same or different dataframes by indexing with the which() function. You can use logical operators to do it across variables.
which(df[,var1] == df[,var1] &
df[,var2] == df[,var2])
The which() function will return an index of rows that meat the functions criteria. If you want it to return rows from your dataframe you can do something like this:
df[
which(df[,var1] == df[,var1] &
df[,var2] == df[,var2])
,]
This will call the row numbers in df that meet your criteria.
selectdoes? Here is a good read for how to program withdplyr.