[R] is that possible to graph 4 dimention plot

[Duncan Murdoch]

On 07/10/2009 5:50 PM, gcheer3 wrote:
> Thanks for your reply.
> 
> But I don't think it will really help. My problem is as follows:
> 
> I have 20 observations
> y <- rnorm(N,mean= rep(th[1:2],N/2),sd=th[3])
> 
> I have a loglikelihood function for 3 variables mu<-(mu1,mu2) and sig
>         loglike <- function(mu,sig){
>         temp<-rep(0,length(y))
>         for (i in 1:(length(y)))
>         {
>        
> temp[i]<-log((1/2)*dnorm(y[i],mu[1],sig)+(1/2)*dnorm(y[i],mu[2],sig))}
>         return(sum(temp))
>          }
> 
> for example
>> mu<-c(1,1.5)
>> sig<-2
>> loglike(mu,sig)
> [1] -34.1811
> 
> I am interested how mu[1], mu[2], and sig changes, will effect the
> loglikelihood surface. At what values of mu and sig will make loglikelihood
> the maximum and at what values of mu and sig will make loglikelihood has
> local max (smaller hills) and at what values of mu and sig the loglikelihood
> is flat , etc. 
> 
> I tried contour3d also, seems doesn't work

I haven't seen any replies to this.  One explanation would be that 
everyone was turned off (as I was) by the rude remark above.

On this list, before saying that something "doesn't work", it's polite 
to give a simple, nicely formatted, self-contained reproducible example 
of what went wrong, and to ask whether it is your error or an error in 
the package.  Taking that approach will usually result in someone 
pointing out your error (and fixing your code); sometimes it will result 
in a package author agreeing it's a bug, and fixing it.

Duncan Murdoch

> 
> Thanks for any advice
> 
> 
> Ryan-50 wrote:
>>> Suppose there are 4 variables
>>> d is a function of a , b and c
>>> I want to know how a, b and c change will make d change
>>> It will be straightforward to see it if we can graph the d surface
>>>
>>> if d is only a function of a and b, I can use 'persp' to see the surface
>>> of
>>> d. I can easily see at what values of a and b, d will get the maxium or
>>> minium or multiple modes, etc
>>>
>>> But for 4 dimention graph, is there a way to show the surface of d
>>> Will use color help
>>>
>>> Thanks a lot
>> Not sure what your data looks like, but you might also 
>> consider looking at a 2 dimensional version.  See ?coplot
>> for example:
>>
>> coplot(lat ~ long | depth * mag, data = quakes)
>>
>> Or you can make 2 or 3-dimensional plots using the lattice 
>> package conditioning on some of the variables - e.g. d ~ a | b * c,
>> etc.  
>>
>> If a, b, and c are "continuous", you can use equal.count.  Here is
>> an uninteresting example, considering a, b, and c as points along
>> a grid:
>>
>> a <- b <- c <- seq(1:10)
>> dat <- data.frame(expand.grid(a, b, c))
>> names(dat) <- letters[1:3]
>>
>> dat$d <- with(dat, -(a-5)^2 - (b-5)^2 - (c-5)^2)
>>
>> library(lattice)
>> # 2-d:
>> xyplot(d ~ a | equal.count(b)*equal.count(c), data=dat, type="l")
>> # etc.
>>
>> # 3-d:
>> contourplot(d ~ a * b | equal.count(c), data=dat)
>> wireframe(d ~ a * b | equal.count(c), data=dat)
>>
>> ______________________________________________
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>> 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.
>>
>>
>