[R] recursive term
Hi r-users;
I have this values:
eign_val <- c(137.810447,3.538721,2.995161,1.685670)
alp <- 1.6549 ; lamda <- eign_val
lamda_m <- min(lamda)
First I calculated manually:
delta0 <- 1
delta1 <- alp*delta0*(4-lamda_m*(1/lamda[1]+1/lamda[2]+1/lamda[3]+1/lamda[4]))
delta1
delta2 <- (alp/2)*(delta1*(delta1/alp) + delta0*((1-lamda_m/lamda[1])^2+
(1-lamda_m/lamda[2])^2+(1-lamda_m/lamda[3])^2+(1-lamda_m/lamda[4])^2))
delta2
delta3 <- (alp/3)*(delta2*(delta1/alp) + delta1*((1-lamda_m/lamda[1])^2+
(1-lamda_m/lamda[2])^2+(1-lamda_m/lamda[3])^2+(1-lamda_m/lamda[4])^2)
+ delta0*((1-lamda_m/lamda[1])^3+
(1-lamda_m/lamda[2])^3+(1-lamda_m/lamda[3])^3+(1-lamda_m/lamda[4])^3))
delta3
c(delta1,delta2,delta3)
> c(delta1,delta2,delta3)
[1] 3.224772 6.391966 10.091279
Then I wrote this the following code:
term <- function(i, lamda, lamda_m)
{sum(sapply(lamda, function(lamda, lamda_m,i) ((1-lamda_m/lamda)^i),
lamda_m, i))}
sm <- sapply(1:N, term, lamda, lamda_m);sm
#now calculate the deltas
k1 <- 3+1
delta <- rep(1, k1);delta
delta_calc <- function(k1, delta, sm, alp)
{ k <- k1-1
alp/k*sum(sapply(1:k, function(i, delta, sm, k1) (sm[i]*delta[k1-i]), delta,
sm, k1))
}
delta[2:k1] <- sapply(2:k1, delta_calc, delta, sm, alp);delta[2:k1]
> delta[2:k1] <- sapply(2:k1, delta_calc, delta, sm, alp);delta[2:k1]
[1] 3.224772 2.804775 2.526796
I could not trace why I the answers are different.
I hope somebody can help me with this.
Thank you so much for your help.
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Re: [R] recursive term
you might try the following.
Pochhammer_n <- function (a,b,c,n) {
if(n==0) return(1)
return(a*b*Pochhammer_n(a+1, b+1, c+1, n-1)/(c*n))
}
hypergeo_sum <- function (a,b,c,z,n) {
comb_sum <- 0
for (i in 0:n) {
comb_sum <- comb_sum + Pochhammer_n(a,b,c,i)*z^i
}
return(comb_sum)
}
hypergeo_sum2 <- function (a,b,c,z,n) {
comb <- rep(1,n+1)
for (i in 2:(n+1)){
comb[i] <- comb[i-1]*(a+i-2)*(b+i-2)*z/((i-1)*(c+i-2))
}
return(sum(comb))
}
system.time(hypergeo_sum (1.25,1.75,1.25,0.5,300))
system.time(hypergeo_sum2(1.25,1.75,1.25,0.5,300))
On Dec 10, 4:28 pm, Roslina Zakaria wrote:
> Hi,
>
> I would like to write a function for this formula:
> F(a,b,c,z)=1+(ab)/(1!c)+ +(a(a+1)b(b+1))/(2!c(c+1))+
> +(a(a+1)(a+2)b(b+1)(b+2))/(3!c(c+1)(c+2))+…
>
> I wrote this function but not sure what is not right:
>
> hypergeo_sum <- function (a,b,c,z,n)
> { for (i in 1:n)
> { aa <- 1+(a*b*z)/c
> aa[i] <- (aa-1)*(a+i)*(b+i)*z/((i+1)*(c+i))
> comb_sum <- aa + aa[i]+ aa[i+2]
> }
> comb_sum}
>
>
> hypergeo_sum (1.25,1.75,1.25,0.5,3)
>
> output:> hypergeo_sum (1.25,1.75,1.25,0.5,3)
>
> [1] 2.394531 NA 1.039062
>
>
> The answer should be 2.852539.
>
> Or can you suggest any R book that I can refer to. Thank you so much for your
> help.
>
> __
> r-h...@r-project.org mailing listhttps://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guidehttp://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
__
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.
[R] recursive term
Hi,
I would like to write a function for this formula:
F(a,b,c,z)=1+(ab)/(1!c)+ +(a(a+1)b(b+1))/(2!c(c+1))+
+(a(a+1)(a+2)b(b+1)(b+2))/(3!c(c+1)(c+2))+…
I wrote this function but not sure what is not right:
hypergeo_sum <- function (a,b,c,z,n)
{ for (i in 1:n)
{ aa <- 1+(a*b*z)/c
aa[i] <- (aa-1)*(a+i)*(b+i)*z/((i+1)*(c+i))
comb_sum <- aa + aa[i]+ aa[i+2]
}
comb_sum
}
hypergeo_sum (1.25,1.75,1.25,0.5,3)
output:
> hypergeo_sum (1.25,1.75,1.25,0.5,3)
[1] 2.394531 NA 1.039062
The answer should be 2.852539.
Or can you suggest any R book that I can refer to. Thank you so much for your
help.
__
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.
