Thanks, I'll try that.
Regarding your question "Why are you using assignments to indicate the
return values of functions?",
I'd probably answer that it is a matlab vice... But I'll change my habits
soon enough!
Best regards,
Eduardo Horta
On Tue, Nov 16, 2010 at 12:27 PM, Erich Neuwirth <
erich.neuwi...@univie.ac.at> wrote:
> Some remarks:
> Why are you using assignments to indicate the return values of functions?
> This is R idiom:
> > f<-function(u){
> > f<-0
> > for (j in 1:4){
> > f<-f+coeff[j]*(zeta(j)(u))
> > }
> > f
> > }
> >
>
> If you only want the inner product of 2 vector, "outer" probably is an
> overkill.
>
> g <- function(u){
> sum(coeff * zeta(1:4)(u))
> }
>
> should be enough.
>
> And plot(g) does not work because g is not vectorized.
>
> plot(Vectorize(g))
>
> will work
>
> On Nov 16, 2010, at 1:18 AM, 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)
> > 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]]
> >
> > ______________________________________________
> > R-help@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
> --
> Erich Neuwirth, University of Vienna
> Faculty of Computer Science
> Center for Computer Science Didactics and Learning Research
> Visit our SunSITE at http://sunsite.univie.ac.at
> Phone: +43-1-4277-39902 Fax: +43-1-4277-39459
>
>
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