[R] Null values In R.

[Daniel Malter]

Hi, for your cor() command you will want to specify the "use" argument as
either "complete.obs" or as "pairwise.complete.obs". The difference between
the two is that the former only uses those observations for which ALL
information in "a" is available, whereas the latter uses information that is
available for all pairwise comparisons between variables in "a". For the
example below, use="c" would exclude observations 6 and 5, whereas use="p"
would exclude observations 6 and 5 for correlations between x and y, and x
and z, but it would only exclude observation 5 for the correlation between y
and z

x=c(1,2,3,4,5,NA)
y=c(2,3,3.5,4.75,NA,7)
z=c(5,8,7,6,NA,11)

a=data.frame(x,y,z)

cor(a)
cor(a,use="c")
cor(a,use="p")

Cheers,
Daniel


-------------------------
cuncta stricte discussurus
-------------------------

-----Ursprüngliche Nachricht-----
Von: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] Im
Auftrag von paul murima
Gesendet: Tuesday, December 02, 2008 11:33 PM
An: r-help at r-project.org
Cc: r-help at stat.math.ethz.ch
Betreff: [R] Null values In R.

Hi everyone.

I am having problems with NULL values. I understand in R one can command the
program to skip null values.
Can some one help me on the command line for that.
Do i enter is as part of the string in:
a<- read.table("filename.csv", header = T, row.names=1, sep=",");

My problem is largely when i attempt to use correlation for my data...
xcc <- cor(a);

The  error i get is as follows

Error in cor(a) : missing observations in cov/cor In addition: Warning
message:
In cor(a) : NAs introduced by coercion


Regards

Paul Murima

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