estimate a truncated normal distribution with only top tail of data of that distribution in r
I am trying to fit a truncated normal distribution to a data, however my problem is I only have top tail of the data/distribution (and I wouldn't know what percentile they are because I dont know about the real distribution's mean and variance yet), by which I want to construct back the truncated normal distribution and get it's estimated mean and variance. The package I used was fitdistrplus::fitdistr.
The codes I tried are as following:
dtnorm.trun1 <- function(x, mean, sd, a= 8.414596, b=Inf)
dnorm(x, mean, sd)/(pnorm(b,mean,sd)-pnorm(a,mean,sd))
ptnorm.trun1 <- function(x, mean, sd, a= 8.414596, b=Inf)
(pnorm(x, mean, sd)-pnorm(a,mean,sd))/(pnorm(b,mean,sd)-pnorm(a,mean, sd))
fit <- fitdistr(data, dtnorm.trun1, method="Nelder-Mead", start=list(mean=-24, sd=21))
I'm doing this practice for replication, so I expect I should be getting fitted mean of -24 and sd of 21, and the real data was truncated at 8.414596. With different starting values and different estimation method, I won't be getting my expected result. I'm really confused about this. Thank you in advance for any suggestion and advise.
r
asked Nov 21 '18 at 21:09
C.DmC.Dm
11
add a comment |
I am trying to fit a truncated normal distribution to a data, however my problem is I only have top tail of the data/distribution (and I wouldn't know what percentile they are because I dont know about the real distribution's mean and variance yet), by which I want to construct back the truncated normal distribution and get it's estimated mean and variance. The package I used was fitdistrplus::fitdistr.
The codes I tried are as following:
dtnorm.trun1 <- function(x, mean, sd, a= 8.414596, b=Inf)
dnorm(x, mean, sd)/(pnorm(b,mean,sd)-pnorm(a,mean,sd))
ptnorm.trun1 <- function(x, mean, sd, a= 8.414596, b=Inf)
(pnorm(x, mean, sd)-pnorm(a,mean,sd))/(pnorm(b,mean,sd)-pnorm(a,mean, sd))
fit <- fitdistr(data, dtnorm.trun1, method="Nelder-Mead", start=list(mean=-24, sd=21))
I'm doing this practice for replication, so I expect I should be getting fitted mean of -24 and sd of 21, and the real data was truncated at 8.414596. With different starting values and different estimation method, I won't be getting my expected result. I'm really confused about this. Thank you in advance for any suggestion and advise.
r
asked Nov 21 '18 at 21:09
C.DmC.Dm
11
2
This is probably a better question for Cross Validated since you seem to be concerned with statistical estimation rather than programming.
– MrFlick
Nov 21 '18 at 21:14
@MrFlick thank you for editing and the suggestion, I will post the question there too. But I also was wondering is it because I understood this package incorrectly or use it wrong..
– C.Dm
Nov 21 '18 at 21:56
add a comment |
I am trying to fit a truncated normal distribution to a data, however my problem is I only have top tail of the data/distribution (and I wouldn't know what percentile they are because I dont know about the real distribution's mean and variance yet), by which I want to construct back the truncated normal distribution and get it's estimated mean and variance. The package I used was fitdistrplus::fitdistr.
The codes I tried are as following:
dtnorm.trun1 <- function(x, mean, sd, a= 8.414596, b=Inf)
dnorm(x, mean, sd)/(pnorm(b,mean,sd)-pnorm(a,mean,sd))
ptnorm.trun1 <- function(x, mean, sd, a= 8.414596, b=Inf)
(pnorm(x, mean, sd)-pnorm(a,mean,sd))/(pnorm(b,mean,sd)-pnorm(a,mean, sd))
fit <- fitdistr(data, dtnorm.trun1, method="Nelder-Mead", start=list(mean=-24, sd=21))
I'm doing this practice for replication, so I expect I should be getting fitted mean of -24 and sd of 21, and the real data was truncated at 8.414596. With different starting values and different estimation method, I won't be getting my expected result. I'm really confused about this. Thank you in advance for any suggestion and advise.
r
asked Nov 21 '18 at 21:09
C.DmC.Dm
11
I am trying to fit a truncated normal distribution to a data, however my problem is I only have top tail of the data/distribution (and I wouldn't know what percentile they are because I dont know about the real distribution's mean and variance yet), by which I want to construct back the truncated normal distribution and get it's estimated mean and variance. The package I used was fitdistrplus::fitdistr.
The codes I tried are as following:
dtnorm.trun1 <- function(x, mean, sd, a= 8.414596, b=Inf)
dnorm(x, mean, sd)/(pnorm(b,mean,sd)-pnorm(a,mean,sd))
ptnorm.trun1 <- function(x, mean, sd, a= 8.414596, b=Inf)
(pnorm(x, mean, sd)-pnorm(a,mean,sd))/(pnorm(b,mean,sd)-pnorm(a,mean, sd))
fit <- fitdistr(data, dtnorm.trun1, method="Nelder-Mead", start=list(mean=-24, sd=21))
I'm doing this practice for replication, so I expect I should be getting fitted mean of -24 and sd of 21, and the real data was truncated at 8.414596. With different starting values and different estimation method, I won't be getting my expected result. I'm really confused about this. Thank you in advance for any suggestion and advise.
r
r
asked Nov 21 '18 at 21:09
C.DmC.Dm
11
asked Nov 21 '18 at 21:09
C.DmC.Dm
11
edited Nov 21 '18 at 22:39
C.Dm
asked Nov 21 '18 at 21:09
C.DmC.Dm
11
asked Nov 21 '18 at 21:09
C.DmC.Dm
11
asked Nov 21 '18 at 21:09
C.DmC.Dm
11
11
2
This is probably a better question for Cross Validated since you seem to be concerned with statistical estimation rather than programming.
– MrFlick
Nov 21 '18 at 21:14
@MrFlick thank you for editing and the suggestion, I will post the question there too. But I also was wondering is it because I understood this package incorrectly or use it wrong..
– C.Dm
Nov 21 '18 at 21:56
add a comment |
2
This is probably a better question for Cross Validated since you seem to be concerned with statistical estimation rather than programming.
– MrFlick
Nov 21 '18 at 21:14
@MrFlick thank you for editing and the suggestion, I will post the question there too. But I also was wondering is it because I understood this package incorrectly or use it wrong..
– C.Dm
Nov 21 '18 at 21:56
2
2
This is probably a better question for Cross Validated since you seem to be concerned with statistical estimation rather than programming.
– MrFlick
Nov 21 '18 at 21:14
This is probably a better question for Cross Validated since you seem to be concerned with statistical estimation rather than programming.
– MrFlick
Nov 21 '18 at 21:14
@MrFlick thank you for editing and the suggestion, I will post the question there too. But I also was wondering is it because I understood this package incorrectly or use it wrong..
– C.Dm
Nov 21 '18 at 21:56
@MrFlick thank you for editing and the suggestion, I will post the question there too. But I also was wondering is it because I understood this package incorrectly or use it wrong..
– C.Dm
Nov 21 '18 at 21:56
add a comment |
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2
This is probably a better question for Cross Validated since you seem to be concerned with statistical estimation rather than programming.
– MrFlick
Nov 21 '18 at 21:14
@MrFlick thank you for editing and the suggestion, I will post the question there too. But I also was wondering is it because I understood this package incorrectly or use it wrong..
– C.Dm
Nov 21 '18 at 21:56