Thanks! Seems to work just fine!
Best regards,
Eduardo Horta
On Mon, Nov 15, 2010 at 10:37 PM, David Winsemius <dwinsem...@comcast.net>wrote:
>
> On Nov 15, 2010, at 7:18 PM, Eduardo de Oliveira Horta wrote:
>
> Hello,
>>
>> I was trying to build some functions which I would like to integrate over
>> an
>> interval using the function 'integrate' from the 'stats' package. As an
>> example, please consider the function
>>
>> h(u)=sin(pi*u) + sqrt(2)*sin(pi*2*u) + sqrt(3)*sin(pi*3*u) + 2*sin(pi*4*u)
>>
>> Two alternative ways to 'build' this function are as in f and g below:
>>
>> coeff<-sqrt(1:4)
>>
>> zeta<-function(i) {force(i); function(u){
>> zeta<-sqrt(2)+sin(pi*i*u)
>> }}
>>
>> f<-function(u){
>> f<-0
>> for (j in 1:4){
>> f<-f+coeff[j]*(zeta(j)(u))
>> }
>> f<-f
>> }
>>
>> g<-function(u){
>> g<-crossprod(coeff,zeta(1:4)(u))
>> }
>>
>> Obviously, f and g are equivalent, but in the actual code I am writing, g
>> is
>> much faster. However, I can't seem to integrate (neither to plot) g. In
>> fact, these are the error messages I get:
>>
>> print(f(.1))
>>>
>> [1] 4.443642
>>
>>> print(g(.1))
>>>
>> [,1]
>> [1,] 4.443642
>>
>> Everything ok until here... but...
>>
>> When using plot(), I get this:
>>
>> plot(f) #plots, as expected.
>>> plot(g)
>>>
>>
> Try vectorizing g()
>
>
>
> g<-function(u){
> g<-crossprod(coeff,zeta(1:4)(u))
> }
>
> gV <- Vectorize(g)
>
> integrate(gV,0,1)
>
> ## 9.696303 with absolute error < 2.5e-13
>
> You didn't say what you thought the analytic answer might be so I cannot
> check it.
>
> --
> David.
>
> Error in crossprod(coeff,zeta(1:4)(u)) : arguments not compatible
>> Besides that: Warning message:
>> In pi * i * u :
>> longer object length is not a multiple of shorter object length
>>
>> When using integrate(), I get this:
>>
>> integrate(f,0,1)
>>>
>> 1.004172 with absolute error < 2.5e-13
>>
>>> integrate(g,0,1)
>>>
>> Error in crossprod(coeff,zeta(1:4)(u)) : arguments not compatible
>> Besides that: Warning message:
>> In pi * i * u :
>> longer object length is not a multiple of shorter object length
>>
>>>
>>>
>> I have already tried some simple 'solutions', for example to set
>> g<-function(u){
>> vec1<-drop(coeff)
>> vec2<-drop(zeta(1:4)(u))
>> g<-drop(crossprod(coeff,zeta(1:4)(u)))
>> }
>>
>> as well as using the %*% operation, but these won't solve my problem.
>>
>> Any suggestions would be welcome. Thanks in advance,
>>
>> Eduardo Horta
>>
>> [[alternative HTML version deleted]]
>>
>
> David Winsemius, MD
> West Hartford, CT
>
>
[[alternative HTML version deleted]]
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