On 2/7/2008 11:40 AM, Don MacQueen wrote:
> Hello,
>
> I am having difficulty figuring out how to use functions in the
> reshape package to perform a wide to long transformation
>
> I have a "wide" dataframe whose columns are like this example:
>
> id1 id2 subject treat height weight age
>
> id1 and id2 are unique for each row
> subject and treat are not unique for each row
> height, weight, and age are different types of measurements made on
> each unique combination of subject and treatment
>
> I want to reshape to a long format which will look like this:
>
> id1 id2 subject treat measurement.type value
>
> where
>
> measurement.type identifies the type of measurement, i.e. 'height',
> 'weight', 'age'
> value contains the values of those measurements
> and the other variables are replicated as necessary
Does something like this work for you?
df <- data.frame(id1 = c(1,2,3),
id2 = c(4,5,6),
subject = runif(3),
treat = runif(3),
height = runif(3),
weight = runif(3),
age = runif(3))
library(reshape)
melt(df, measure.var = c("height","weight","age"))
id1 id2 subject treat variable value
1 1 4 0.4736760 0.02221288 height 0.09290354
2 2 5 0.1708840 0.84465476 height 0.70660286
3 3 6 0.6955085 0.56084004 height 0.52761841
4 1 4 0.4736760 0.02221288 weight 0.08853412
5 2 5 0.1708840 0.84465476 weight 0.85745906
6 3 6 0.6955085 0.56084004 weight 0.29902097
7 1 4 0.4736760 0.02221288 age 0.91842595
8 2 5 0.1708840 0.84465476 age 0.93592277
9 3 6 0.6955085 0.56084004 age 0.01587108
> To put it another way, can I use reshape() to transform my original
> dataframe, which has 45 rows, into a "long" form that has 3*45 = 135
> rows: 45 rows for height, 45 for weight, 45 for age, with the other
> variables carried along as is within each set of 45, and a new
> variable that identifies the type of measurement in each row of the
> long form, i.e., 'height' in 45 rows, 'weight' in 45 rows, and 'age'
> in 45 rows.
>
> I know it's not difficult to do this with explicit looping, using
> rbind(), but it seems like reshape() is a natural tool. But I'm not
> getting it, so I'd appreciate some help.
>
> (in case anyone is wondering whether it makes sense to do this,
> height, weight, and age are just examples; it makes more sense with
> my actual measurements)
>
> Thanks
> -Don
--
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