Hi all,
I had several replies that provided a solution to my previous query.
Using plyr it seems to work (Thanks Dennis Murphy and Arun)
library(plyr)
ddply(DF, .(SPEC_CODE), mutate, RA = 10 * sum(AI)/sum(Time))
This one nearly works just need to invert the SumAI and Sum Survey time
so that SumAI/SumTime provides the correct answer.
res<- mutate(ddply(dat1,.(SPEC_CODE,Location_name),function(x)
colSums(x[,-c(1:3,6)])),SumAIbySumST=Survey_Time/AI,Std.SumAIbySumST=10*SumAIbySumST)
Tnx all for the help,
Bruce
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