[R] sampling one random frame from each unique trial?

[Daniel Malter]

Hi, take the following example and proceed accordingly.

Name=c("Miller","Miller","Miller","Miller","Smith","Smith","Smith","Smith")
X=rnorm(8)
Year=rep(2000:2003,2)

d=data.frame(Name,X,Year)

#Row indices
rows=1:dim(d)[1]

#Which Name occupies which rows?
#"Name" would be your "file"
w=function(x){which(Name%in%unique(x))}
samplefrom=tapply(Name,Name,w)

#Sample one row index for each Name and
#give the data frame d for these row indices
f=function(x){sample(x,1)}
d[unlist(lapply(samplefrom,f)),]

HTH,
Daniel

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