Re: [R] Help with package reshape, wide to long

From: Don MacQueen <macq_at_llnl.gov>
Date: Thu, 7 Feb 2008 10:36:36 -0800

It does indeed.

Thank you, Chuck.

-Don

At 1:25 PM -0500 2/7/08, Chuck Cleland wrote:
>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
>
>--
>Chuck Cleland, Ph.D.
>NDRI, Inc.
>71 West 23rd Street, 8th floor
>New York, NY 10010
>tel: (212) 845-4495 (Tu, Th)
>tel: (732) 512-0171 (M, W, F)
>fax: (917) 438-0894

-- 
--------------------------------------
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA
925-423-1062

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Received on Thu 07 Feb 2008 - 18:38:24 GMT

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