R help - Nov 2005 - Error in integrate

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

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