[R] trouble understanding why ...=="NaN" isn't true

Bert Gunter gunter.berton at gene.com
Wed May 30 00:39:58 CEST 2007

1. "NaN" is a character string, **not** NaN; hence is.nan("NaN") yields

2. Please read the docs!  ?NaN explicitly says:

"Do not test equality to NaN, or even use identical, since systems typically
have many different NaN values."

Bert Gunter
Genentech Nonclinical Statistics

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Andrew Yee
Sent: Tuesday, May 29, 2007 3:33 PM
To: r-help at stat.math.ethz.ch
Subject: [R] trouble understanding why ...=="NaN" isn't true

I have the following data:

> dataset[2,"Sample.227"]
[1]    NaN
1558 Levels: -0.000 -0.001 -0.002 -0.003 -0.004 -0.005 -0.006 -0.007 -0.008-
0.009 ...  2.000

However, I'm not sure why this expression is coming back as FALSE:

> dataset[2,"Sample.227"]=="NaN"


> dataset[2,"Sample.227"]==NaN
[1] NA

It seems that since "NaN" is represented as a character, this expression
=="NaN" should be TRUE, but it's returning as FALSE.


	[[alternative HTML version deleted]]

R-help at stat.math.ethz.ch mailing list
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

More information about the R-help mailing list