You can create a list of functions then use subscripting. E.g.: funvec <- c(sin, cos, tan)
for(i in 1:3) { print(funvec[[i]](pi/6)) } Just create the list with the different functions that you want to call, then subscript that list with your n_r variable. You can also look at ?switch, but I think the list of functions may work better for you. On Sat, Mar 19, 2016 at 7:17 AM, Mahmoud via R-help <r-help@r-project.org> wrote: > Dear R Experts > > I've a function which involves multiple summations, and the number of > summations depends on a > random variable named (n-r), where n is known but r is random and r<n. > > So, if , for example , n-r=3, the function is: > >>n_r=3 >>fx=function(x)sum(sapply(1:n_r, function(j1) {sum(sapply(1:(j1), >>function(j2){sum(sapply(1:(j2), >>function(j3){(j1>j2)*(j2>j3)/(x+exp(tc[j1]+tc[j2]+tc[j3])^4}))}))}))} > > The value of r will be generated from a simulation process, so in one > iteration r may be equal to 0, and in another iteration it might be equal to > 2 and so on, and accordingly (n-r) is either 1, 2, or 3. And this makes the > body of the summation different every time. > > > Here's my trail code in the simple case when n=3: > > library(nleqslv) > N=100;n=3 > a=matrix(0,nrow=N,ncol=1) > for(i in 1:N){ > tc=matrix(0, nrow=n, ncol=1) > t=matrix(0, nrow=n, ncol=1) > c=matrix(0,nrow=n,ncol=1) > for(j in 1: n){ > t[j]=rexp(1,rate=3) > > c[j]=rexp(1, rate =2) > if (t[j]>=c[j]) {tc[j]=t[j]} > } > n_r=nrow(tc) > if(n_r==1){fx=function(x)sum(sapply(1:n-3, function(j1){1/(x+exp(tc[j1]))^4})) > a[i]=nleqslv(0.5, fx)$x > } > if(n_r==2){fx=function(x)sum(sapply(1:n-2, > function(j1){sum(sapply(1:(j1),function(j2){(j1>j2)/(x+exp(tc[j1]+tc[j2]))^4}))})) > a[i]=nleqslv(0.5, fx)$x > } > if(n_r==3){fx=function(x)sum(sapply(1:n, function(j1) {sum(sapply(1:(j1), > function(j2){sum(sapply(1:(j2), > function(j3){(j1>j2)*(j2>j3)/(x+exp(tc[j1]+tc[j2]+tc[j3]))^4}))}))})) > a[i]=nleqslv(0.5, fx)$x > } > } > > Is there any other way to write a loop that could be executed for any value > of r instead of putting the if () statement for each single value of r , as > n may take large values reaching 30, for instance. > > Any help or recommendation for a reference that can help me would be > appreciated . > Thank you > Mahmoud Farid > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.