> On Feb 11, 2016, at 9:20 AM, C W <tmrs...@gmail.com> wrote: > > 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?
So what's the difficulty? It's rather like the Dirac function. > integrate( function(x) dnorm(x, sd=0.00001), -.0001,0.0001) 1 with absolute error < 7.4e-05 -- David. > > 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. David Winsemius Alameda, CA, USA ______________________________________________ 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.
