Re: [R] calculate quantiles of a custom function
Am Dienstag, 3. Januar 2012, 19:51:36 schrieb Prof. Dr. Matthias Kohl:
D - AbscontDistribution(d = function(x) dbeta(x, 2, 6) + dbeta(x,6,2),
low = 0, up = 1, withStand = TRUE)
Dear all,
thank you all again for your help.
So, summing up, (in case this might be useful to other beginners - like me)
this is how it can be done:
library(distr)
dcustom - function(x) {
(dbeta(x,2,6) + dbeta(x,6,2))/2# I need to divide by 2 to get 1 as
# result of
integration;
}
pcustom - function(x) {
integrate(dmyspeaker,0,x)$value
}
D - AbscontDistribution(d = dcustom, low = 0, up = 1, withStand = TRUE)
qcustom - function(x){
q(D)(x)
}
Best,
Gerhard
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Re: [R] calculate quantiles of a custom function
FWIW, the integral of a mixture density is the same mixture of the
CDFs, so you can use the pbeta functions:
pcustom - function(x) (pbeta(x,2,6) + pbeta(x,6,2))/2
albyn
Quoting Gerhard felds...@gmx.net:
Am Dienstag, 3. Januar 2012, 19:51:36 schrieb Prof. Dr. Matthias Kohl:
D - AbscontDistribution(d = function(x) dbeta(x, 2, 6) + dbeta(x,6,2),
low = 0, up = 1, withStand = TRUE)
Dear all,
thank you all again for your help.
So, summing up, (in case this might be useful to other beginners - like me)
this is how it can be done:
library(distr)
dcustom - function(x) {
(dbeta(x,2,6) + dbeta(x,6,2))/2# I need to divide by 2 to get 1 as
# result of
integration;
}
pcustom - function(x) {
integrate(dmyspeaker,0,x)$value
}
D - AbscontDistribution(d = dcustom, low = 0, up = 1, withStand = TRUE)
qcustom - function(x){
q(D)(x)
}
Best,
Gerhard
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[R] calculate quantiles of a custom function
Hi,
I guess that my problem has an obvious answer, but I have not been able to
find it.
Suppose I create a custom function, consisting of two beta-distributions:
myfunction - function(x) {
dbeta(x,2,6) + dbeta(x,6,2)
}
How can I calculate the quantiles of myfunction?
I have not seen any continous function treated in the docs, and applying the
quantile function gives me an error (since it seems only to be defined on
lists and atoms).
Thank you in advance,
Gerhard
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Re: [R] calculate quantiles of a custom function
Gerhard:
Strictly speaking, it's quantiles of a custom distribution, not function.
There may be some way to handle your example easily, but, in general,
you would need to solve the resulting integral equation. This is hard
-- closed form solutions rarely exist; good approximations require
work.
So a standard approach is: simulate. Indeed, many simulation tricks
(under the rubric of variance reduction) have been developed exactly
for such monte carlo integration. Consult a good reference or
knowledgeable person for details.
-- Bert
On Tue, Jan 3, 2012 at 4:24 AM, Gerhard felds...@gmx.net wrote:
Hi,
I guess that my problem has an obvious answer, but I have not been able to
find it.
Suppose I create a custom function, consisting of two beta-distributions:
myfunction - function(x) {
dbeta(x,2,6) + dbeta(x,6,2)
}
How can I calculate the quantiles of myfunction?
I have not seen any continous function treated in the docs, and applying the
quantile function gives me an error (since it seems only to be defined on
lists and atoms).
Thank you in advance,
Gerhard
__
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
--
Bert Gunter
Genentech Nonclinical Biostatistics
Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
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Re: [R] calculate quantiles of a custom function
On Jan 3, 2012, at 7:24 AM, Gerhard wrote:
Hi,
I guess that my problem has an obvious answer, but I have not been
able to
find it.
Suppose I create a custom function, consisting of two beta-
distributions:
myfunction - function(x) {
dbeta(x,2,6) + dbeta(x,6,2)
}
Given the symmetry of the beta function, I suspect that dividing by
two would make that a real distribution.
How can I calculate the quantiles of myfunction?
You could build a CDF using 'integrate'.
I have not seen any continous function treated in the docs, and
applying the
quantile function gives me an error (since it seems only to be
defined on
lists and atoms).
There is also a family of packages, all of whose names begin with
distr. They provide a variety of facilities for developing new
distributions, both discrete and continuous.
--
David Winsemius, MD
West Hartford, CT
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Re: [R] calculate quantiles of a custom function
Am Dienstag, 3. Januar 2012, 11:05:11 schrieben Sie: The quick way is to look at the structure with 'str': str(integrate(myfunction,0,.9)) List of 5 $ value : num 1.85 $ abs.error : num 2.05e-14 $ subdivisions: int 1 $ message : chr OK $ call: language integrate(f = myfunction, lower = 0, upper = 0.9) - attr(*, class)= chr integrate The longer way would be to look at the help)integrate) page where the Value section would have told you that a list with named components was returned: integrate(myfunction,0,.9)$value [1] 1.850299 In this instance you could also probably use 'cumsum' (which is just doing the numerical integration by hand plot(cumsum( myfunction(seq(0,1,by=0.001)))/ sum(myfunction(seq(0,1,by=0.001)) ) ) Thanks a lot; now I now where I need to look for help before bothering you again. Best, Gerhard I need to hand on the value to another function, and then I get an error message, because the output of integrate is not a numerical argument. I have not seen any continous function treated in the docs, and applying the quantile function gives me an error (since it seems only to be defined on lists and atoms). There is also a family of packages, all of whose names begin with distr. They provide a variety of facilities for developing new distributions, both discrete and continuous. That looks quite frightening. But if it turns out to be necessary. But a good way to improve you knowledge of statistical concepts. Thank you, Gerhard David Winsemius, MD West Hartford, CT __ 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.
Re: [R] calculate quantiles of a custom function
Gerhard wrote
Suppose I create a custom function, consisting of two beta-distributions:
myfunction - function(x) {
dbeta(x,2,6) + dbeta(x,6,2)
}
How can I calculate the quantiles of myfunction?
Thank you in advance,
Gerhard
Gehard, if do you want to know the quantiles of the new distribution created
by myfunction. Maybe you can also do:
x - seq(0,1,.01) # insert your 'x'
q - myfunction(x)
# And:
quantile(x)
0% 25% 50% 75% 100%
0.00 1.476177 2.045389 2.581226 2.817425
# This gives the sample quantiles. You can also look foward to simulations
(like Bert Gunter had suggested) to know better the properties of
distributions quantiles obtained after 'myfunction'.
-
Victor Delgado
cedeplar.ufmg.br P.H.D. student
www.fjp.mg.gov.br reseacher
--
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Re: [R] calculate quantiles of a custom function
VictorDelgado wrote quantile(x) Correcting to quantile(q) - Victor Delgado cedeplar.ufmg.br P.H.D. student www.fjp.mg.gov.br reseacher -- View this message in context: http://r.789695.n4.nabble.com/calculate-quantiles-of-a-custom-function-tp4256887p4257575.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.
Re: [R] calculate quantiles of a custom function
What do quantiles mean here? If you have a mixture density, say
myf - function(x,p0) p0*dbeta(x,2,6) + (1-p0)*dbeta(x,6,2)
then I know what quantiles mean. To find the Pth quantile use uniroot
to solve for the x such that myf(x,p0) - P =0.
albyn
Quoting VictorDelgado victor.m...@fjp.mg.gov.br:
Gerhard wrote
Suppose I create a custom function, consisting of two beta-distributions:
myfunction - function(x) {
dbeta(x,2,6) + dbeta(x,6,2)
}
How can I calculate the quantiles of myfunction?
Thank you in advance,
Gerhard
Gehard, if do you want to know the quantiles of the new distribution created
by myfunction. Maybe you can also do:
x - seq(0,1,.01) # insert your 'x'
q - myfunction(x)
# And:
quantile(x)
0% 25% 50% 75% 100%
0.00 1.476177 2.045389 2.581226 2.817425
# This gives the sample quantiles. You can also look foward to simulations
(like Bert Gunter had suggested) to know better the properties of
distributions quantiles obtained after 'myfunction'.
-
Victor Delgado
cedeplar.ufmg.br P.H.D. student
www.fjp.mg.gov.br reseacher
--
View this message in context:
http://r.789695.n4.nabble.com/calculate-quantiles-of-a-custom-function-tp4256887p4257551.html
Sent from the R help mailing list archive at Nabble.com.
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Re: [R] calculate quantiles of a custom function
On 03/01/2012 1:33 PM, Albyn Jones wrote:
What do quantiles mean here? If you have a mixture density, say
myf- function(x,p0) p0*dbeta(x,2,6) + (1-p0)*dbeta(x,6,2)
then I know what quantiles mean. To find the Pth quantile use uniroot
to solve for the x such that myf(x,p0) - P =0.
You would want to integrate first...
Duncan Murdoch
albyn
Quoting VictorDelgadovictor.m...@fjp.mg.gov.br:
Gerhard wrote
Suppose I create a custom function, consisting of two beta-distributions:
myfunction- function(x) {
dbeta(x,2,6) + dbeta(x,6,2)
}
How can I calculate the quantiles of myfunction?
Thank you in advance,
Gerhard
Gehard, if do you want to know the quantiles of the new distribution created
by myfunction. Maybe you can also do:
x- seq(0,1,.01) # insert your 'x'
q- myfunction(x)
# And:
quantile(x)
0% 25% 50% 75% 100%
0.00 1.476177 2.045389 2.581226 2.817425
# This gives the sample quantiles. You can also look foward to simulations
(like Bert Gunter had suggested) to know better the properties of
distributions quantiles obtained after 'myfunction'.
-
Victor Delgado
cedeplar.ufmg.br P.H.D. student
www.fjp.mg.gov.br reseacher
--
View this message in context:
http://r.789695.n4.nabble.com/calculate-quantiles-of-a-custom-function-tp4256887p4257551.html
Sent from the R help mailing list archive at Nabble.com.
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Re: [R] calculate quantiles of a custom function
Dear Gerhard,
you could also use package distr; e.g.
library(distr)
## use generating function AbscontDistribution
D - AbscontDistribution(d = function(x) dbeta(x, 2, 6) + dbeta(x,6,2),
low = 0, up = 1, withStand = TRUE)
## quantiles
q(D)(seq(0,1,0.1))
Best
Matthias
On 03.01.2012 19:33, Albyn Jones wrote:
What do quantiles mean here? If you have a mixture density, say
myf - function(x,p0) p0*dbeta(x,2,6) + (1-p0)*dbeta(x,6,2)
then I know what quantiles mean. To find the Pth quantile use uniroot to
solve for the x such that myf(x,p0) - P =0.
albyn
Quoting VictorDelgado victor.m...@fjp.mg.gov.br:
Gerhard wrote
Suppose I create a custom function, consisting of two
beta-distributions:
myfunction - function(x) {
dbeta(x,2,6) + dbeta(x,6,2)
}
How can I calculate the quantiles of myfunction?
Thank you in advance,
Gerhard
Gehard, if do you want to know the quantiles of the new distribution
created
by myfunction. Maybe you can also do:
x - seq(0,1,.01) # insert your 'x'
q - myfunction(x)
# And:
quantile(x)
0% 25% 50% 75% 100%
0.00 1.476177 2.045389 2.581226 2.817425
# This gives the sample quantiles. You can also look foward to
simulations
(like Bert Gunter had suggested) to know better the properties of
distributions quantiles obtained after 'myfunction'.
-
Victor Delgado
cedeplar.ufmg.br P.H.D. student
www.fjp.mg.gov.br reseacher
--
View this message in context:
http://r.789695.n4.nabble.com/calculate-quantiles-of-a-custom-function-tp4256887p4257551.html
Sent from the R help mailing list archive at Nabble.com.
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Prof. Dr. Matthias Kohl
www.stamats.de
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Re: [R] calculate quantiles of a custom function
Am Dienstag, 3. Januar 2012, 08:50:44 schrieb VictorDelgado: VictorDelgado wrote quantile(x) Correcting to quantile(q) - Dear Victor, thank you for your answer. Best, Gerhard Victor Delgado cedeplar.ufmg.br P.H.D. student www.fjp.mg.gov.br reseacher -- View this message in context: http://r.789695.n4.nabble.com/calculate-quantiles-of-a-custom-function-tp42 56887p4257575.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. __ 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.
Re: [R] calculate quantiles of a custom function
right. replace dbetas with pbetas.
albyn
Quoting Duncan Murdoch murdoch.dun...@gmail.com:
On 03/01/2012 1:33 PM, Albyn Jones wrote:
What do quantiles mean here? If you have a mixture density, say
myf- function(x,p0) p0*dbeta(x,2,6) + (1-p0)*dbeta(x,6,2)
then I know what quantiles mean. To find the Pth quantile use uniroot
to solve for the x such that myf(x,p0) - P =0.
You would want to integrate first...
Duncan Murdoch
albyn
Quoting VictorDelgadovictor.m...@fjp.mg.gov.br:
Gerhard wrote
Suppose I create a custom function, consisting of two beta-distributions:
myfunction- function(x) {
dbeta(x,2,6) + dbeta(x,6,2)
}
How can I calculate the quantiles of myfunction?
Thank you in advance,
Gerhard
Gehard, if do you want to know the quantiles of the new
distribution created
by myfunction. Maybe you can also do:
x- seq(0,1,.01) # insert your 'x'
q- myfunction(x)
# And:
quantile(x)
0% 25% 50% 75% 100%
0.00 1.476177 2.045389 2.581226 2.817425
# This gives the sample quantiles. You can also look foward to simulations
(like Bert Gunter had suggested) to know better the properties of
distributions quantiles obtained after 'myfunction'.
-
Victor Delgado
cedeplar.ufmg.br P.H.D. student
www.fjp.mg.gov.br reseacher
--
View this message in context:
http://r.789695.n4.nabble.com/calculate-quantiles-of-a-custom-function-tp4256887p4257551.html
Sent from the R help mailing list archive at Nabble.com.
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