R help - Feb 2005 - NA's in if statement

Hello,

I am having trouble dealing with NA values in if statements such as:
i<-1
for(i in 1:length(dat$wdir)){
if (dat$wspd[i]==0){
dat$wdir[i]<-0
}
}

I get the following error due to the presence of NS values in the data:
Error in if (dat$wspd[i] == 0) { : missing value where TRUE/FALSE needed

Sorry if this is an old question but I was unable to resolve this from the
info on na.action etc. or old archives.

Thank you for any suggestions,

Vera Lindsay

Some careful use of is.na() may help.
Either by using it to remove NA values or as part of the if statement.
 
Or:
 
my.wdir <- na.omit(dat$wdir)
for(i in 1:length(my.wdir)) {
 
#etc

	-----Original Message----- 
	From: r-help-bounces at stat.math.ethz.ch on behalf of lindsayv at unbc.ca 
	Sent: Fri 2/11/2005 9:34 PM 
	To: r-help at stat.math.ethz.ch 
	Cc: 
	Subject: [R] NA's in if statement
	
	

	Hello,
	
	I am having trouble dealing with NA values in if statements such as:
	i<-1
	for(i in 1:length(dat$wdir)){
	if (dat$wspd[i]==0){
	dat$wdir[i]<-0
	}
	}
	
	I get the following error due to the presence of NS values in the data:
	Error in if (dat$wspd[i] == 0) { : missing value where TRUE/FALSE needed
	
	Sorry if this is an old question but I was unable to resolve this from the
	info on na.action etc. or old archives.
	
	Thank you for any suggestions,
	
	Vera Lindsay
	
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