Hello,
Like others have said, the root does depend on the seed but not by much.
Here is a loop finding the roots for seeds from 1 to 10,000.
I have defined a variable n == 1000 instead of having the calls to rnorm
depend on a hard-coded constant.
ff <- function(zz){
inner = vector("numeric", length = s)
for(k in 1:s){
inner[k]=(1- lam*((1+b[k]*((zz-thr)/a[k]))^(-1/b[k])))
}
answer = mean(inner) - (1 - (1/r))
return(answer)
}
n <- 1000
s <- n
lam <- 0.15
thr <- 70
r <- 10
up_lims <- 112.5 # found by trial and error to be nice most
# of the time, see mean(ok) below
out_list <- vector("list", length = 1e4)
for(i in seq_along(out_list)) {
# give the user feedback
if(i %% 100 == 0) print(i)
set.seed(i)
a <- rnorm(n, 110, 5)
b <- rnorm(n, -0.3, 0.4)
out_list[[i]] <- tryCatch(
uniroot(ff, lower = 0, upper = up_lims),
error = function(e) e
)
}
ok <- !sapply(out_list, inherits, 'error')
mean(ok)
#[1] 0.9978
root <- sapply(out_list[ok], '[[', 'root')
hist(root)
Hope this helps,
Rui Barradas
Às 15:37 de 04/08/2022, Ebert,Timothy Aaron escreveu:
And one last edit.
Rstudio Environment shows out$root as 112. However, if I then print
out$root I get 111.5303 which is much closer to the right answer.
Entering values for ff, I can work out the answer to slightly more
than 111.53030196.
Regards,
Tim
-----Original Message-----
From: Ebert,Timothy Aaron <teb...@ufl.edu>
Sent: Thursday, August 4, 2022 10:28 AM
To: Ebert,Timothy Aaron <teb...@ufl.edu>; Md. Moyazzem Hossain
<hossai...@juniv.edu>; J C Nash <profjcn...@gmail.com>
Cc: r-help mailing list <r-help@r-project.org>
Subject: RE: [R] Need help
I wish I could edit my earlier reply.
ff(144.43) returns 0.03142121, but ff(144.44) returns NaN.
ff(12) returns -0.1468287
out=uniroot(ff, lower=12, upper =144) does not have errors.
out is a list of 5.
$root is 112
$f.root is 1.09e-08
$iter is 5
$Init.it is NA
$estim.prec is 6.1e-05
Is this working?
Regards,
Tim
-----Original Message-----
From: R-help <r-help-boun...@r-project.org> On Behalf Of Ebert,Timothy
Aaron
Sent: Thursday, August 4, 2022 10:09 AM
To: Md. Moyazzem Hossain <hossai...@juniv.edu>; J C Nash
<profjcn...@gmail.com>
Cc: r-help mailing list <r-help@r-project.org>
Subject: Re: [R] Need help
[External Email]
A few issues
1) What does this function do? If you describe the problem and goal
there might be a better answer. We appreciate seeing that you have
attempted a solution, but you have trapped us all in blindly following
your attempt.
2) This is an error checking phase of programming. Setting the seed is
a good idea. Just remember to unset the seed after finishing the
debugging phase.
3) In uniroot you call the function, but the function expects an
argument (zz) that is not provided, and there is no default.
4) I set.seed(42), and entered ff(12) getting an answer of -0.1468287.
Is this the expected result?
Regards,
Tim
-----Original Message-----
From: R-help <r-help-boun...@r-project.org> On Behalf Of Md. Moyazzem
Hossain
Sent: Thursday, August 4, 2022 9:50 AM
To: J C Nash <profjcn...@gmail.com>
Cc: r-help mailing list <r-help@r-project.org>
Subject: Re: [R] Need help
[External Email]
Dear JN,
Thanks.
I do not check whether the function actually crosses zero or not.
However, by assumption, the value would be greater than zero.
Hossain
On Thu, Aug 4, 2022 at 2:40 PM J C Nash <profjcn...@gmail.com> wrote:
Have you checked that your function actually crosses zero?
You should also set a seed if you want a reproducible result.
JN
On 2022-08-04 09:30, Md. Moyazzem Hossain wrote:
Dear R Experts,
I hope that you are doing well.
I am facing a problem to find out the value of the following
function. I need help in this regard.
#####
a=rnorm(1000, 110, 5)
b = rnorm(1000, -0.3, 0.4)
s = length(a)
lam=0.15
thr=70
r= 10
ff = function(zz){
inner = vector("numeric", length = s)
for(k in 1:s){
inner[k]=(1- lam*((1+b[k]*((zz-thr)/a[k]))^(-1/b[k])))
}
answer = mean(inner)- (1- (1/r))
return(answer)
}
########
out=uniroot(ff, lower = 0, upper = 10000 )$root out
########### Error ########
Error in uniroot(ff, lower = 0, upper = 10000) :
f.upper = f(upper) is NA
Please help me. Thanks in advance.
Take care.
Hossain
--
Best Regards,
Md. Moyazzem Hossain
Associate Professor
Department of Statistics
Jahangirnagar University
Savar, Dhaka-1342, Bangladesh
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