How to delete data according to certain criteria in R

Question

I want to delete datapoints if their value are above a certain value but below another, but I simply cannot figure out how to do it in R.

I want to remove data points if x<0.5 and y>2, but both criteria needs to be met.

Thanks in advance!

Rorschach · Accepted Answer · 2013-05-30T12:33:09.327

2

dat <- data.frame(x=runif(100,0,2), y=runif(100,1,4))
todrop <- which(dat$x <0.5 & dat$y>2)
dat <- dat[-todrop,]

edited May 30 '13 at 12:33

answered May 30 '13 at 12:07

Rorschach

Thank you, but it is not working. Only data for which both criteria (i.e. x<0.5 and y>2) are met should be removed - any idea about how to do that? thanks!! – R-gal May 30 '13 at 12:15
@R-gal please read http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example Show some code and tell us "what actually is not working" – Beasterfield May 30 '13 at 12:35
Thanks Beasterfield, I'm new in this, sorry. I have a dataset with 500 datapoints, where I want to remove some of them because they are obviously wrong. I have tried both suggestions, but they remove too many points, i.e. they remove ALL points where x<0.5 even though the criteria for y isn't met. Does it make sense? Will try to post the codes I used as well.. – R-gal May 30 '13 at 12:44

score 2 · Answer 2 · edited May 23 '17 at 11:45

2

If you want to use this programmatically, the use of subset should be avoided (see Why is `[` better than `subset`? for details).

Instead, you could go with the data.frame syntax:

dat[ dat$x >= 0.5 & dat$y <= 2, ]

Reading of ? "[.data.frame" is an absolute must to any R beginner.

edited May 23 '17 at 11:45

Community

answered May 30 '13 at 12:13

Beasterfield

2 Answers2