[R] difference in pairs ?

[Peter Ehlers]

On 2011-02-22 12:51, Vlatka Matkovic Puljic wrote:
> Well, it should be difference by ID and TIME for q1:
> something like:
> for ID 1187
> in TIME 1                       q1=3
> and TIME 2 (for same ID) q1=3
> so diff would be 3-3=0
>
> TIME   ID  q1
>     1  1187  3
>     1  1187  3
>
> And I don't know how to make R to find pairs and calculate diff?

Maybe plyr can do the job:

  require(plyr)
  ddply(dd, .(ID), summarize,
     dq1 = q1[TIME == 1] - q1[TIME == 2],
     dq2 = q2[TIME == 1] - q2[TIME == 2])

(I don't know how you're planning to use Wilcoxon on the result.)

Peter Ehlers

>
> 2011/2/21 Dennis Murphy<djmuser at gmail.com>
>
>> Hi:
>>
>> Assuming dd is the name of your data frame,
>>
>>> dd$diff<- with(dd, q2 - q1)
>>> dd
>>    TIME   ID q1 q2 diff
>> 1    1 1187  3  2   -1
>> 2    1 1706  3  3    0
>>
>> 3    1 1741  2  4    2
>> 4    2 1187  3  2   -1
>> 5    2 1706  3  3    0
>> 6    2 1741  2  4    2
>>
>> is one way to do it.
>>
>> HTH,
>> Dennis
>>
>> On Mon, Feb 21, 2011 at 11:05 AM, Vlatka Matkovic Puljic<
>> v.matkovic.puljic at gmail.com>  wrote:
>>
>>> Dear all,
>>>
>>> I want to perform paired Wilcoxon signed ranks test on my data.
>>> I have pairs defined by ID and TIME variables.
>>>
>>> How can I calculate difference in variables q1, q2 in each pair?
>>>
>>> TIME ID q1 q2
>>> 1 1187 3 2
>>> 1 1706 3 3
>>> 1 1741 2 4
>>> 2 1187 3 2
>>> 2 1706 3 3
>>> 2 1741 2 4
>>>
>>> Please, any clue!
>>> :)
>>>
>>>
>>> --
>>> **************************
>>> Vlatka Matkovic Puljic
>>> +32/ 485/ 453340
>>>
>>>         [[alternative HTML version deleted]]
>>>
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>>
>>
>
>