Peter, Thank you very much!
2011/6/26 Peter Ehlers <ehl...@ucalgary.ca>
> On 2011-06-26 06:34, li li wrote:
>
>> Thank you all for the answering.
>> Sorry I did not state the problem clearly. I want to take the
>> integration with respect to mu, not x.
>> For example, f1 should have been a function of x after integrating mu
>> out of f(x, mu) which is the following:
>> f(x, mu)=dnorm(x, mean=mu, sd=1)*dnorm(mu, mean=2, sd=1).
>>
>
> So you probably want something like:
>
> h <- function(mu, x) dnorm(x, mu, 1) * dnorm(mu, 2, 1)
> f1 <- function(x)
> integrate(function(mu, x) h(mu, x), -Inf, Inf, x)$value
>
> In your original formulation (below), all you have
> to do is change
>
> {integrand <- function (x, mu){
>
> to
>
> {integrand <- function (mu, x){
>
>
> Peter Ehlers
>
>
>> Thank you!
>> Hannah
>>
>>
>> f1<- function(x)
>>
>> {integrand <- function (x, mu){
>>
>> dnorm(x, mean=mu, sd=1)*dnorm(mu, mean=2, sd=1)
>>
>> }
>>
>> integrate(integrand, -Inf, Inf,x)$val
>>
>> }
>>
>>
>> f2<- function(x)
>>
>> {integrand <- function (x, mu){
>>
>> dnorm(x, mean=mu, sd=1)*mu^2*dnorm(mu, mean=2, sd=1)
>>
>> }
>>
>> integrate(integrand, -Inf, Inf,x)$val
>>
>> }
>>
>>
>>
>> 2011/6/25 Peter Ehlers <ehl...@ucalgary.ca <mailto:ehl...@ucalgary.ca>>
>>
>>
>> On 2011-06-25 08:48, li li wrote:
>>
>> Hi all,
>> Can anyone please take a look at the following two functions.
>> The answer does not seem to be right.
>> Thank you very much!
>>
>> f1<- function(x)
>>
>> {integrand<- function (x, mu){
>>
>> dnorm(x, mean=mu, sd=1)*dnorm(mu, mean=2, sd=1)
>>
>> }
>>
>> integrate(integrand, -Inf, Inf,x)$val
>>
>> }
>>
>>
>> f2<- function(x)
>>
>> {integrand<- function (x, mu){
>>
>> dnorm(x, mean=mu, sd=1)*mu^2*dnorm(mu, mean=2, sd=1)
>>
>> }
>>
>> integrate(integrand, -Inf, Inf,x)$val
>>
>> }
>>
>>
>> Your x and mu will get mightily confused.
>> The argument x in f1 is in fact used as the argument mu
>> in integrand() because, as the help page clearly indicates,
>> additional arguments follow the lower/upper limits in integrate().
>>
>> A cleaner version of what you're doing is the following:
>>
>> f1 <- function(mu){
>>
>> integrand <- function (x, mu){
>> dnorm(x, mean=mu, sd=1) * dnorm(mu, mean=2, sd=1)
>> }
>> integrate(integrand, -Inf, Inf, mu)[["value"]]
>> }
>>
>> But then again, you could just evaluate dnorm(mu, 2, 1).
>> So I suspect that you want something different.
>>
>> Ditto for f2.
>>
>> Peter Ehlers
>>
>>
>>
>> [[alternative HTML version deleted]]
>>
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