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<djmu...@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.pul...@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

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