[R] When creating a data frame with data.frame() transforms "integers" into "factors"

[Bert Gunter]

Huh?

> z <- sample(1:10,30,rep=TRUE)
> tbl <- table(z)
> tbl
z
 1  2  3  4  5  6  7  8  9 10
 4  3  2  6  3  3  2  2  2  3
> data.frame(z)
    z
1   5
2   2
3   4
4   1
5   6
6   4
7  10
8   4
9   3
10  8
11 10
12  4
13  3
14  9
15  2
16  2
17  6
18  1
19  4
20  7
21  9
22 10
23  7
24  5
25  5
26  6
27  8
28  1
29  1
30  4
> sapply(data.frame(z),class)
        z
"integer"

Your error: you used df['posts']  . You should have used df[,'posts'] .

The former is a data frame. The latter is a vector. Read the
"Introduction to R tutorial" or ?"[" if you don't understand why.

-- Bert

-- Bert

On Sat, May 25, 2013 at 12:36 PM, António Camacho <toinobc at gmail.com> wrote:
> Hello
>
>
> I am novice to R and i was learning how to do a scatter plot with R using
> an example from a website.
>
> My setup is iMac with Mac OS X 10.8.3, with R 3.0.1, default install,
> without additional packages loaded
>
> I created a .csv file in vim with  the following content
> userID,user,posts
> 1,user1,581
> 2,user2,281
> 3,user3,196
> 4,user4,150
> 5,user5,282
> 6,user6,184
> 7,user7,90
> 8,user8,74
> 9,user9,45
> 10,user10,20
> 11,user11,3
> 12,user12,1
> 13,user13,345
> 14,user14,123
>
> i imported the file into R using : ' df <- read.csv('file.csv')
> to confirm the data types i did : 'sappily(df, class) '
> that returns "userID" --> "integer" ; "user" ---> "factor" ; "posts" --->
> "integer"
> then i try to create another data frame with the number of posts and its
> frequencies,
> so i did: 'postFreqCount<-data.frame(table(df['posts']))'
> this gives me the postFreqCount data frame with two columns, one called
> 'Var1' that has the number of posts each user did, and another collumn
> 'Freq' with the frequency of each number of posts.
> the problem is that if i do : 'sappily(postFreqCount['Var1'],class)' it
> returns "factor".
> So the data.frame() function transformed a variable that was "integer"
> (posts) to a variable (Var1) that has the same values but is "factor".
> I want to know how to prevent this from happening. How do i keep the values
> from being transformed from "integer" to "factor" ?
>
> Thank you for your help
>
> António
>
>         [[alternative HTML version deleted]]
>
>
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>



-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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Phone: 467-7374
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