CODEWITHSUNDEEP
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Prafulla
Prafulla

Reputation: 585

how to get class of a variable in R using loop?

I have data frame in R with four columns and I am trying to get class of each variable using for loop, depending on a class of variable I could write a further code. Below is the data frame.

   var1 var2 var3 var4
1     1    a    a    s
2     2    g    a    s
3     3    b         s
4     4    n    s    s
5    NA    m    f    f
6     6    r    g    v
7     7    t         b
8     8         j     
9     9    y    i    g
10   10    h    i    t

As of now I have tried below code but it is giving NULL for a class of variable

for (i in names(df)){
  print(names(df[i]))
  name <- names(df[i])
  print(class(df$name))
}

Result with above code:

[1] "var1"
[1] "NULL"
[1] "var2"
[1] "NULL"
[1] "var3"
[1] "NULL"
[1] "var4"
[1] "NULL"

Expecting Result

    [1] "var1"
    [1] "integer"
    [1] "var2"
    [1] "factor"
    [1] "var3"
    [1] "factor"
    [1] "var4"
    [1] "integer"

Requesting your help.

Upvotes: 1

Views: 2348

Answers (2)

Thom Quinn
Thom Quinn

Reputation: 308

Since data.frames are really just a list of columns, I do this often using lapply:

lapply(df, class)

As for the for loop you have in the example, when you call df$name, R is trying to find the column called "name". Instead, you want df[, name]:

for (i in names(df)){
  name <- names(df[i])
  print(name)
  print(class(df[, name]))
}

Upvotes: 4

Derek Corcoran
Derek Corcoran

Reputation: 4102

Using mtcars as an example:

for (i in names(mtcars)){
    print(names(mtcars[i]))
    name <- names(mtcars[i])
    print(class(mtcars[,i]))
    }

Upvotes: 1

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