[R] Error in integrate

[Thomas Lumley]

On Wed, 16 Nov 2005, Vivien W. Chen wrote:

> Hi!
>
> I am a beginner of R. I am trying to calculate integrate and draw a 
> graph of the output, but just kept on getting error messages. I list my 
> program and error message below. Please help. Many Thanks!
>
> =======================
> + > a<--11
>> b<-0.1
>> c<-0.012
>> x<-0:110

This is harmless but suspicious -- this x is completely unrelated to the x 
in integrand()

>> t<-0:15
>> integrand<-function(x) {exp(-exp(a-c*t)*(exp(b*x)-exp(c*x))/(b-c))}

The problem is that x is a vector of whatever length integrate() decides 
to pass, but t is a vector of length 16.  This mismatch of lengths is 
going to cause a problem.

>> cal<-integrate(integrand,0,Inf)
> Error in integrate(integrand, 0, Inf) : evaluation of function gave a result of wrong length
> In addition: Warning message:
> longer object length
>        is not a multiple of shorter object length in: -exp(a - c * t) * (exp(b * x) - exp(c * x))
>> plot(cal~t, xlab="Time", ylab="Pop at t")
> Error in model.frame(formula, rownames, variables, varnames, extras, extranames,  :
>        invalid variable type
> ===========================
>
> - Vivien Chen -
> 	[[alternative HTML version deleted]]
>
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Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle