repeat expression several times in R

Question

In R, I want to find out the effect of character string length on computation time of a certain operation. For this, I need random character strings of different lengths. All I can think of now is:

cases1 <- letters[sample(15)] cases2 <- paste(letters[sample(15)], letters[sample(15)], sep="") cases3 <- paste(letters[sample(15)], letters[sample(15)], letters[sample(15)], sep="")

How do I automate that? I don't want to keep copypasting... Or does anyone have a better idea?

akrun · Accepted Answer · 2014-12-10 18:00:59Z

2

Try

 n <- 3 do.call(`paste0`,as.data.frame(replicate(n, letters[sample(15)])))

If you want say 1:3

 n1 <- 1:3 lapply(n1, function(.n) do.call(`paste0`, as.data.frame(replicate(.n, letters[sample(15)]))))

Or as @Berry showed in the comments

 apply(replicate(3, letters[sample(15)]), MARGIN=1, paste, collapse="")

edited Dec 10, 2014 at 18:00

answered Dec 10, 2014 at 17:51

akrun

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2 Comments

Berry Boessenkool Over a year ago

Oh Yes. replicate is exactly what I need!! Thanks for making my day!

Berry Boessenkool Over a year ago

People scared of do.call might want also want to try apply(replicate(3, letters[sample(15)]), MARGIN=1, paste, collapse="")

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