[R] number of individuals where X=0 during all periods (longitudinal data)

[David L Carlson]

Spend a little time with aggregate()

?aggregate

-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of najuzz
Sent: Monday, December 22, 2014 7:45 AM
To: r-help at r-project.org
Subject: [R] number of individuals where X=0 during all periods (longitudinal data)

#Hi guys, 

#I would like to count the number of individuals that receive X=0 troughout
their observational period.
#example dataset:

ID<-c(1,1,1,1,2,2,3,3,3)
X<-c(0,1,2,1,0,0,0,0,0)
Time<-c(1,2,3,4,1,2,1,2,3)
Test<-data.frame(ID,X,Time)

# Individuals 2 and 3 have x=0 during all their periods. The count should
hence equal to two. I simply have 
# no clue how R could solve this for me. As an addon, I would also like to
know the number of individuals  #that report X=0 during all periods plus
have at least 3 weeks of observations. The answer would be one in #this
sample datset.

#Thank you



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