[R] Linear Model "NA" Value Test

[David Winsemius]

On Sep 21, 2009, at 4:50 PM, David Winsemius wrote:

>
> On Sep 21, 2009, at 4:38 PM, Douglas M. Hultstrand wrote:
>
>> Hello,
>>
>> I am deriving near real-time liner relationships based on 5-min
>> precipitation data, sometimes the non-qced data result in a slope  
>> of NA.  I
>> am trying to read the coefficient (in this example x) to see if it  
>> is equal
>> to NA, if it is equal to NA assign it a value of 1.  I am having  
>> trouble
>> with the if statement not recognizing the coefficient or "NA" value  
>> in the
>> test.
>>
>> Any thoughts, I supplied a really basic example below.
>>
>> Thank you,
>> Doug
>>
>> #####################
>> ###### Example ######
>> #####################
>> x=c(1,1,1)
>> y=c(1,1,1)
>> fit <- lm(y~x) fit
>>
>> Call:
>> lm(formula = y ~ x)
>> Coefficients:
>> (Intercept)            x
>> 1           NA
>>
>> coef <- coef(fit) fit$coef[[2]]
>> [1] NA
>> if("fit$coef[[2]]" == "NA") {.cw = 1}

And furthermore, don't surround your expressions with quotes unless  
that exactly what you wnat to test. Almost surely you wanted to see if  
fit$coef[[2]] were equal to <something>  rather than "fit$coef[[2]]".

> That would test for equality to the string composed of "N" and "A"  
> but not for NA. (Nothing "equals" NA. )
>
> ?is.na
>

David Winsemius, MD
Heritage Laboratories
West Hartford, CT