I don't know if I understand (small example with R command wouuld help),

but, assuming your data.frame is called 'df'

subset(df, ID %in% ID_list)

Question, is ID_list a "list" or a vector, and are they really "numbers"

or "factors"?

Kyle. wrote:

> R-help:

>

> I have a variable ("ID_list") containing about 1800 unique numbers, and a

> 143066x29 data frame. One of the columns ("ID") in my data frame contains a

> list of ids, many of which appear more than once. I'd like to find the

> subset of my data frame for which "ID" matches one of the numbers in

> "ID_list." I'm pretty sure I could write a function to do this--something

> like:

>

> dataSubset<-function(df, id_list){

> tmp = data.frame()

> for(i in id_list){

> for(j in 1:dim(df)[1]){

> if(i==df$ID[j]){

> tmp<-data.frame(df[j,])

> }

> }

> }

> tmp

> }

>

> but this seems inefficient. As I understand it, the subset function won't

> really solve my problem, but it seems like there must be something out there

> that will that I must be forgetting. Does anyone know of a way to solve this

> problem in an efficient way? Thanks!

>

>

> Kyle H. Ambert

> Graduate Student, Department of Medical Informatics & Clinical Epidemiology

> Oregon Health & Science University

>

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>

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>

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http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.