Hi,
(a) sum() and mean() have a na.rm argument that should be set to TRUE.
(b) let's try with an example:
x <- c(1:5, NA, NA, 6:10, NA)
x[is.na(x)] <- 0 ## replace NAs by 0
HTH,
Ivan
Le 12/1/2010 10:00, Iasonas Lamprianou a ?crit :> Dear all,
> i have spent a lot of time trying to solve this problem, but I am sure that
> there must be a simple solution. So, as a last resort, I am coming back to
you
> again. I have a dataset with some (almost random) values in many variables.
Lets
> say that the dataset represents the scores of students to test questions.
What I
> need to do is to sum the scores for each student. However, wherever there
is a
> missing (NA) value, I cannot get the total score. How can I compute the
total
> score and the average per question (a) by ignoring the missing responses,
(b) by
> assuming that a missing response is a zero?
> Thank you for the response
>
>
> Dr. Iasonas Lamprianou
>
>
>
>
> Assistant Professor (Educational Research and Evaluation)
> Department of Education Sciences
> European University-Cyprus
> P.O. Box 22006
> 1516 Nicosia
> Cyprus
> Tel.: +357-22-713178
> Fax: +357-22-590539
>
>
>
>
> Honorary Research Fellow
> Department of Education
> The University of Manchester
> Oxford Road, Manchester M13 9PL, UK
> Tel. 0044 161 275 3485
> iasonas.lamprianou at manchester.ac.uk
>
>
>
>
>
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
--
Ivan CALANDRA
PhD Student
University of Hamburg
Biozentrum Grindel und Zoologisches Museum
Abt. S?ugetiere
Martin-Luther-King-Platz 3
D-20146 Hamburg, GERMANY
+49(0)40 42838 6231
ivan.calandra at uni-hamburg.de
**********
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