I want to do numerical integration w.r.t. mu: P(mu) × N(mu, 0.00001) Because the variance is small, it results in density like: 7.978846e+94
Is there any good suggestion for this? Thanks so much! On Thu, Feb 11, 2016 at 9:14 AM, C W <tmrs...@gmail.com> wrote: > Wow, thank you, that was very clear. Let me give it some more runs and > investigate this. > > On Thu, Feb 11, 2016 at 12:31 AM, William Dunlap <wdun...@tibco.com> > wrote: > >> Most of the mass of that distribution is within 3e-100 of 2. >> You have to be pretty lucky to have a point in sequence >> land there. (You will get at most one point there because >> the difference between 2 and its nearest neightbors is on >> the order of 1e-16.) >> >> seq(-2,4,len=101), as used by default in curve, does include 2 >> but seq(-3,4,len=101) and seq(-2,4,len=100) do not so >> curve(..., -3, 4, 101) and curve(..., -2, 4, 100) will not show the bump. >> The same principal holds for numerical integration. >> >> >> Bill Dunlap >> TIBCO Software >> wdunlap tibco.com >> >> On Wed, Feb 10, 2016 at 6:37 PM, C W <tmrs...@gmail.com> wrote: >> >>> Dear R, >>> >>> I am graphing the following normal density curve. Why does it look so >>> different? >>> >>> # the curves >>> x <- seq(-2, 4, by=0.00001) >>> curve(dnorm(x, 2, 10^(-100)), -4, 4) #right answer >>> curve(dnorm(x, 2, 10^(-100)), -3, 4) #changed -4 to -3, I get wrong >>> answer >>> >>> Why the second curve is flat? I just changed it from -4 to -3. There is >>> no density in that region. >>> >>> >>> Also, I am doing numerical integration. Why are they so different? >>> >>> > x <- seq(-2, 4, by=0.00001) >>> > sum(x*dnorm(x, 2, 10^(-100)))*0.00001 >>> [1] 7.978846e+94 >>> > x <- seq(-1, 4, by=0.00001) #changed -2 to -1 >>> > sum(x*dnorm(x, 2, 10^(-100)))*0.00001 >>> [1] 0 >>> >>> What is going here? What a I doing wrong? >>> >>> Thanks so much! >>> >>> [[alternative HTML version deleted]] >>> >>> ______________________________________________ >>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >>> 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. >>> >> >> > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
