[R] Reformatting dataframe for use with icc()

Frans Marcelissen fransiepansiekevertje at gmail.com
Sat Oct 10 22:56:28 CEST 2015


I think this is what reshape is made for...
Frans
--------------------------------------

rater.id <- c(1, 2, 1, 3, 2, 3)
observation <- c(1, 1, 2, 2, 3, 3)
rating <- c(6, 7, 4, 6, 2, 4)
dat=data.frame(rater.id,observation,rating)

library(reshape)
dat2<-melt(dat, id.vars = c('rater.id','observation'))
cast(dat2,observation~rater.id)
observation  1  2  3
               1  6  7 NA
               2  4 NA  6
               3 NA  2  4

2015-10-10 20:15 GMT+02:00 David L Carlson <dcarlson at tamu.edu>:

> Don't post in html, the list scrambles your tables. Assuming your data
> looks like this
>
> > rater.id <- c(1, 2, 1, 3, 2, 3)
> > observation <- c(1, 1, 2, 2, 3, 3)
> > rating <- c(6, 7, 4, 6, 2, 4)
> > dat <- data.frame(rbind(rater.id, observation, rating))
> > dat
>             X1 X2 X3 X4 X5 X6
> rater.id     1  2  1  3  2  3
> observation  1  1  2  2  3  3
> rating       6  7  4  6  2  4
>
> We need to transpose the data and then use xtabs(). This will work as long
> as there is not more than one rating on an observation by the same rater:
>
> > t(dat)
>    rater.id observation rating
> X1        1           1      6
> X2        2           1      7
> X3        1           2      4
> X4        3           2      6
> X5        2           3      2
> X6        3           3      4
>
> > tbl <- xtabs(rating~observation+rater.id, t(dat))
> > tbl
>            rater.id
> observation 1 2 3
>           1 6 7 0
>           2 4 0 6
>           3 0 2 4
>
> If the 0's are a problem:
>
> > tbl[tbl==0] <- NA
> > print(tbl, na.print=NA)
>            rater.id
> observation    1    2    3
>           1    6    7 <NA>
>           2    4 <NA>    6
>           3 <NA>    2    4
>
>
> David L. Carlson
> Department of Anthropology
> Texas A&M University
>
>
> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Chad
> Danyluck
> Sent: Friday, October 9, 2015 4:02 PM
> To: r-help at r-project.org
> Subject: [R] Reformatting dataframe for use with icc()
>
> Hello,
>
> I want to determine the inter-rater reliability of ratings made from a
> random selection of observers and observations. I plan to use the irr
> package to calculate the ICC, however, my dataframe is not organized in a
> way that the icc() function can handle. The icc() function works with
> dataframes in the following format:
>
>                      rater1 rater2 rater3...
> observation
> 1                           6       7      NA
> 2                           4    NA          6
> 3                         NA       2         4
> ...
>
> My dataframe is organized in the following format:
>
> rater.id               1  2  1  3  2  3 ...
> observation       1  1  2  2  3  3 ...
> rating                 6  7  4  6  2  4 ...
>
> I would like to reformat my dataframe as it is organized in the first
> example but I am not sure how to go about doing this. Any suggestions would
> be appreciated.
>
> Kind regards,
>
> Chad
>
> --
> Chad M. Danyluck, MA
> PhD Candidate, Psychology
> University of Toronto
>
>
>
> “There is nothing either good or bad but thinking makes it so.” - William
> Shakespeare
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> and provide commented, minimal, self-contained, reproducible code.
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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