I have a database here and I need to automatically check which are quantitative variables. My advisor says that I need to use sapply and the is.numeric function and create a code that returns a vector of true and false indicating which variables are numeric.
Could you help me?
This, you will use sapply with the is.numeric function. In summary, sapply will apply to every variable (column) of your data.frame the is.numeric function to know if that is a numeric variable.
Generating a basis for demonstration:
df <- data.frame(numeric1 = 1:10,
factor = factor(c("a", "b")),
character = "texto",
numeric2 = 10:1,
logical = TRUE ,
stringsAsFactors = FALSE)
str(df)
$ numeric1 : int 1 2 3 4 5 6 7 8 9 10
$ factor : Factor w/ 2 levels "a","b": 1 2 1 2 1 2 1 2 1 2
$ character: chr "texto" "texto" "texto" "texto" ...
$ numeric2 : int 10 9 8 7 6 5 4 3 2 1
$ logical : logi TRUE TRUE TRUE TRUE TRUE TRUE ...
Using sapply with is.numeric to generate a vector indicating which columns are numeric:
numericas <- sapply(df, is.numeric)
numericas
numeric1 factor character numeric2 logical
TRUE FALSE FALSE TRUE FALSE
Now you can use this vector to filter the data.frame:
df[,numericas]
numeric1 numeric2
1 1 10
2 2 9
3 3 8
4 4 7
5 5 6
6 6 5
7 7 4
8 8 3
9 9 2
10 10 1