Have you tried vectorizing the inner function? Hint: integrate() calls the integrand vectorwise... in your example, integrate(Vectorize(f),lower=1,upper=2) should do what you expected.
Best, Peter Eddy H. G. Bekkers wrote: > > Hi, > > Could somebody help me with the following. I want to calculate the > integral over an implicit function. I thought to integrate over a function > depending on uniroot. In previous topics I found a thread about finding > the root of an integral. And that works. But the other way around, does > not work. Does R support this? > > I included the following example. The function in the example is very easy > and can be solved explicitly, but when it does not work for such an easy > function it will certainly not work for a more difficult function. First > the root of an integral (which works) and then the integral of a function > dependent on uniroot: > > # Calculating the root of an integral > > a<- function(x,y) > {x-y} > > b<- function(y) > {integrate(a,lower=1,upper=2,y=y)$value} > > d<- uniroot(b,c(0,10))$root > > print(d) > > # Calculating the integral of a function dependent on uniroot > > e<- function(u,v) > {u-v} > > f<- function(v) > {uniroot(e,c(0,10),v=v)$root} > > g<- integrate(f,lower=1,upper=2)$value > > print(g) > > Does anyone have suggestions how to proceed? By the way, the implicit > function I am targeting does have a unique solution, it is only not > explicitly solvable, i.e. in the example above, you cannot solve u as a > function of v explicitly, so as to substitute it in the integrand. > > > Thanks a lot in advance for your help, > > Best regards, > > Eddy Bekkers > Department of Economics > Erasmus University Rotterdam > > ______________________________________________ > 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. > > -- View this message in context: http://www.nabble.com/Integral-implicit-function-tp14201932p14260535.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.