Question on summing rows within nested variable
If you want zero if only one variable:
DF2
sid pid slope 1 1.1 1.1 2 2 1.1 4.1 3 3 1.1 5.1 2 4 2.1 5.1 3 5 3.2 1.2 2 6 3.2 1.7 3
tapply(DF2$slope, DF2$sid, function(x) if(length(x) == 1) 0 else mean(x))
1.1 2.1 3.2 2.333333 0.000000 2.500000
On Fri, Mar 13, 2009 at 6:43 PM, Vedula, Satyanarayana
<svedula at jhsph.edu> wrote:
Hi, I was hoping someone could help figure out how to write code for R to do the below. I have data that looks like below. Variables, sid and pid are strings, slope is numeric. I need R to get me the mean of slopes for all pid's nested within each sid if there are more than one pid's nested within sid. If there is only pid for a sid, like for 2.1 below, I want R to write a 0. In the data below, I want to get the mean of slopes for pid (1.1; 4.1; and 5.1) because they are nested within sid 1.1 and so on. Thanks in advance for any suggestions. Swaroop sid ? ? ? ?pid ? ? ? ?slope 1.1 ? ? ? ?1.1 ? ? ? ?2 1.1 ? ? ? ?4.1 ? ? ? ?3 1.1 ? ? ? ?5.1 ? ? ? ?2 2.1 ? ? ? ?5.1 ? ? ? ?3 3.2 ? ? ? ?1.2 ? ? ? ?2 3.2 ? ? ? ?1.7 ? ? ? ?3 ? ? ? ?[[alternative HTML version deleted]]
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