From: Brian G. Peterson <brian_at_braverock.com>

Date: Tue 17 Oct 2006 - 11:48:53 GMT

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Tue Oct 17 21:52:55 2006

Date: Tue 17 Oct 2006 - 11:48:53 GMT

Torleif Markussen Lunde wrote:

> In a dataset I have length and age for cod. The age, however, is ony

*> given for 40-100% of the fish. What I need to do is to fill inn the NAs
**> in a correct way, so that age has a value for each length. This is to be
**> done for each sample seperately (there are 324 samples), meaning the NAs
**> for sampleno 1 shall be calculated from the known values from sampleno
*

1.

*>
*

> As for example length 55 cm can be both 4 and 5 years, I guess a fish

*> with NA age and length 55 cm should be given a "random" age given a
**> probability for example "55 cm = 4 years has a p=75%, while 55 cm = 4
**> years has a p=25%". Those "p-values" should be calculated from the real
**> data.
**>
**> How can this be done in R, and what is the right way to do it?
*

Given the size of your sample, wouldn't it be more statistically valid to set the age of the NA records to the mean age of records of matching length? I suppose you could also use resampling or a bootstrap, but I'm not sure that adding randomization will give results that are any more statistically valid than using the mean.

Regards,

- Brian

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