[R] Dealing with null values Aggregate function

From: Andrew McFadden <Andrew.McFadden_at_maf.govt.nz>
Date: Tue, 17 May 2011 14:27:14 +1200


Hi R users

I trying to some aggregate statistics on a very large dataset. The null values are causing a problem. I would like to calculate aggregate values for groups. I am just no sure how to deal with the "" I would ideally like them to ignored ie if there is only 1 value over several columns than that value would be the summary statistic.

I have put the following example together to show my problem.

testDF <- data.frame(v1 = c(1,3,5,7,8,3,5,NA,4,5,7,9),

                     v2 = c(11,33,55,77,88,33,55,NA,44,55,77,99),
	

v3=c("red","red","red","red","red","red","blue","blue","blue","blue","bl ue","blue"))

aggregate(x = testDF, by = list(testDF$v3), FUN = "mean")

For this example I would like to get a mean value for red (v1=4.5; v1=5) and blue (v1=49.5; v2=55)

Thank you in advance.

Andy

Andrew McFadden MVS BVSc
Incursion Investigator
Investigation & Diagnostic Centres - Wallaceville Biosecurity New Zealand Ministry of Agriculture and Forestry

Phone 04 894 5600 Fax 04 894 4973 Mobile 029 894 5611 Postal address: Investigation and Diagnostic Centre- Wallaceville Box 40742 Ward St Upper Hutt

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