[R] Warning message in if else statement

[Monica Pisica]

Hi Erik,

Thanks for your answer. I did print the p-value just before the statement and it is only one value – or at least I see only one value ….. that is strange.

I am doing a test and I want to see what is it's p-value ….for example my function "myf" is like that:

myf <- function(m, se, conf.int)
 {
z <- qnorm((1+conf.int)/2)
pval <- (1 - pnorm(abs(m/se)))*2
if (pval==0) p_value <- "<- pval
tst <- data.frame(m/se, p_value, m - z*se, m + z*se)
names(tst) <- c("m/se", "p-value", "C.I.1","C.I.2")
print(tst, quote = F)
}
 
If m = 0.3913681 and se = 0.04628602 pval = 0 so I am testing if pval = 0 and I am reporting a very small number …. Maybe I should report 0 but sincerely I don't quite like it so I rather report a p-values less than 2.2e-16 which is 0 for all practicality – I would say. If I use this function as it is …. No problems, if I incorporate inside a different function so to be used internally I get the warning. Any idea why?

Thanks,

Monica



> Date: Wed, 23 Jul 2008 12:24:55 -0500
> From: iverson at biostat.wisc.edu
> To: pisicandru at hotmail.com
> CC: r-help at r-project.org
> Subject: Re: [R] Warning message in if else statement
>
> Monica -
>
> Monica Pisica wrote:
>> Hi,
>>
>> I am using an if else statement inside a function …. If I use that
>> function I have no problems …. If I use the function with the if else
>> statement inside a second function I get the following waring:
>>
>> Warning message: In if (pval == 0) p_value <- "< 2.2e-16" else
>> p_value <- pval : the condition has length> 1 and only the first
>> element will be used
>
> This means that pval has more than one element, try printing its value
> immediately before the if statement to see what it is and how it got
> that way.
>
> I also might ask what exactly you're doing with 'real p-values' and
> testing whether they equal 0?
>
>>
>> Using the second function I get the expected results, with a real
>> p-value even if it is extremely small, or "
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>>
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enger2_072008