[R] Introduction of NA:s

John Fox jfox at mcmaster.ca
Wed Oct 2 14:02:06 CEST 2002

Dear Patrik,

At 12:01 PM 10/2/2002 +0200, Patrik Waldmann wrote:
>I wonder if someone could help me with the following: I have generated 10 
>000 values from rnorm and now I want to randomly replace 500 of those with 
>NA. The problem is that values indexed between 6-10,16-20,26-30.... only 
>should be considered for replacement. Any suggestions?

There's probably a cleverer way of doing it, but the following should work:

         nums <- 1:10000
         data <- rnorm(10000)
         data[sample(nums[is.element(nums - 10*floor(nums/10), c(0,6:9))], 
500)] <- NA

I hope that this helps,

John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox

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