[R] calculate column means when missing data is present

[Peter Alspach]

Luke

Check

?colMeans  or help(colMeans)

you will see there is an agrument, na.rm, which by default is FALSE -
you need to set it to TRUE.

Peter Alspach


> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Luke Neraas
> Sent: Tuesday, 27 November 2007 1:59 p.m.
> To: r-help
> Subject: [R] calculate column means when missing data is present
> 
> # Hello,
> 
> # I have a matrix that contains some missing values denoted by NA.
> # I would like to calculate the mean for each column and not 
> have the # NA values included.  here is a sample matrix  "X" below.
> 
> 
> c1 <- c(1,4,3,2,NA,2,5,6,4,2)
> c2 <- c(1,3,6,NA,NA,2,9,6,1,2)
> c3 <- c(2,4,2,NA,4,2,NA,6,3,5)
> c4 <- c(2,6,4,NA,4,2,NA,6,1,5)
> c5 <- c(2,3,2,NA,4,2,9,6,NA,5)
> 
> X<-cbind(c1,c2,c3,c4,c5)
> 
> X
> 
> # I have tried a variety of methods to calculate the Column 
> means but each time # i do not get the result i am looking for
> 
> result<-colMeans(X)  # only returns a mean of NA
> 
> 
> X <- X[!is.na(X)]    # Effectively removes the NA values but now I
> cannot calculate Column Means
> 
> #  Below is the result of the column means I am looking for
> 
> result
>        c1   c2    c3   c4    c5
>  [1,] 3.22 3.75  3.5  3.75 4.125
> 
> 
> # any help or ideas would be greatly appreciated
> 
> # thanks in advance
> 
> Luke Neraas
> 
> lukasneraas.r at gmail.com
> 
> University of Alaska Fairbanks
> School of Fisheries and Ocean Sciences
> 11120 Glacier Highway
> UAF Fisheries Division
> Juneau, AK 99801
> 
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> 

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