On Thu, 20 Aug 2009, Tal Galili wrote:
Hello dear R-help group.
My task looks simple, but I can't seem to find a "smart" (e.g: non loop)
solution to it.
Task: I wish to randomize a data.frame by one column, while keeping the
inner-order in the second column as is.
xx[ order( sample( unique( xx$a ) )[ xx$a ] ), ]
HTH,
Chuck
So for example, let's say I have the following data.frame:
xx <-data.frame(a= c(1,2,2,3,3,3,4,4,4,4) ,
b = c(1,1,2,1,2,3,1,2,3,4) )
I would like to shuffle it by column "a", while keeping the order in column
"b".
Here is my "not-smart" way of doing it:
# R example
xx <-data.frame(a= c(1,2,2,3,3,3,4,4,4,4) ,
b = c(1,1,2,1,2,3,1,2,3,4) )
randomize.by.column.a <- function(xx)
{
new.a.order <- sample(unique(xx$a))
new.xx <- NULL
for(i in new.a.order)
{
xx.subset <- xx[ xx$a %in% i ,]
new.xx <- rbind(new.xx , xx.subset)
}
return(new.xx)
}
randomize.by.column.a(xx)
# END of - R example
I would love for a better, faster, way of doing it.
Thanks,
Tal
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My contact information:
Tal Galili
Phone number: 972-50-3373767
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Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:cbe...@tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
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