R help - Aug 2003 - Error on mclust

Hi All,


I am trying to cluster a one-dimensional data (see the file attached) using 
Mclust() but got an error message like:
>Mclust(x)
Error in rep(1, n) : Object "n" not found

When I do a simulation sometimes it works sometimes doesn't.
>Mclust(c(rnorm(50),rnorm(56,-0.5)))
Error in rep(1, n) : Object "n" not found
>Mclust(c(rnorm(56),rnorm(56,-0.5)))
best model: unequal variance with 2 groups

averge/median classification uncertainty: 0.001 / 0

Can anybody help me with this? Thanks.

Weidong

_________________________________________________________________

I can't find the function Mclust(). Which package is it from?

Nonetheless, here are a couple of steps to help you find the problem:
1) Find a reproducable example which ALWAYS recreate your problem (i.e., 
define x so that Mclust(x) gives your error message);
2) Run "debug(Mclust); Mclust(x)" and execute your example step by
step
until you see the error. Hopefully, this will help you find the cause of 
the problem.

If you still can't resolve it, then send us your reproducable example 
(from step 1). Try to use a very small data set that illustrates the 
problem.

HTH,
Jerome

On August 5, 2003 02:16 pm, weidong zhang wrote:
> Hi All,
>
>
> I am trying to cluster a one-dimensional data (see the file attached)
> using
>
> Mclust() but got an error message like:
> >Mclust(x)
>
> Error in rep(1, n) : Object "n" not found
>
> When I do a simulation sometimes it works sometimes doesn't.
>
> >Mclust(c(rnorm(50),rnorm(56,-0.5)))
>
> Error in rep(1, n) : Object "n" not found
>
> >Mclust(c(rnorm(56),rnorm(56,-0.5)))
>
> best model: unequal variance with 2 groups
>
> averge/median classification uncertainty: 0.001 / 0
>
> Can anybody help me with this? Thanks.
>
> Weidong
>
> _________________________________________________________________
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help

Hi,

this goes also to the developer and maintainer of mclust.

Here are some reproducible results:
> set.seed(300)
> x <- c(rnorm(50),rnorm(56,-0.5)) 
> Mclust(x)
Error in rep(1, n) : Object "n" not found
> set.seed(3000)
> y <- c(rnorm(50),rnorm(56,-0.5)) 
> Mclust(y)
 best model: unequal variance with 3 groups

 averge/median classification uncertainty: 0.002 / 0 

Now what's the difference between x and y?
function EMclust works for both, but not summary.EMclust:
> emx <- EMclust(x)
> emx
 BIC:
          E         V
1 -304.8738 -304.8738
2 -314.2134        NA
3 -323.5445        NA
4 -332.8736        NA
5 -342.2043        NA
6 -351.5322        NA
7 -360.8612        NA
8 -370.1896        NA
9 -379.5153        NA
> help(summary.EMclust)
> summary(emx,x)
Error in rep(1, n) : Object "n" not found
> emy <- EMclust(y)
> summary(emy,y)
classification table:

  1   2   3 
100   4   2 

uncertainty (quartiles):
        0%        25%        50%        75%       100% 
0.00000000 0.00000000 0.00000000 0.00000000 0.06683614 

best BIC values:
      V,3       V,2       E,1 
-293.2526 -302.0302 -304.2835 

best model: unequal variance 
> emy
 BIC:
          E         V
1 -304.2835 -304.2835
2 -313.6275 -302.0302
3 -322.9562 -293.2526
4 -332.2631        NA
5 -341.5896        NA
6 -350.8819        NA
7 -352.6121        NA
8 -361.9393        NA
9 -371.2658        NA

Here is the explanation:

For x, one class G=1 is chosen as optimal.
The line rep(1,n) appears in summary.EMclust (which is called by Mclust,
but not by EMclust), but it is called only if G=1 is estimated. 
Indeed, n is not defined (as far as I can see), which is a bug. 

It's possible to work around that bug:
For concrete data analysis, if the error occurs, 
you may assume (and check by application of
EMclust), that G=1 is estimated, which means that you can fit a single
normal distribution, for which you do not need Mclust. 
Otherwise you should get proper results.

Best,
Christian

On Tue, 5 Aug 2003, weidong zhang wrote:
> Hi All,
> 
> 
> I am trying to cluster a one-dimensional data (see the file attached) using
> Mclust() but got an error message like:
> >Mclust(x)
> Error in rep(1, n) : Object "n" not found
> 
> When I do a simulation sometimes it works sometimes doesn't.
> 
> >Mclust(c(rnorm(50),rnorm(56,-0.5)))
> Error in rep(1, n) : Object "n" not found
> 
> >Mclust(c(rnorm(56),rnorm(56,-0.5)))
> 
> best model: unequal variance with 2 groups
> 
> averge/median classification uncertainty: 0.001 / 0
> 
> Can anybody help me with this? Thanks.
> 
> Weidong
> 
> _________________________________________________________________
> 
> 
> 
-- 
***********************************************************************
Christian Hennig
Seminar fuer Statistik, ETH-Zentrum (LEO), CH-8092 Zuerich (currently)
and Fachbereich Mathematik-SPST/ZMS, Universitaet Hamburg
hennig at stat.math.ethz.ch, http://stat.ethz.ch/~hennig/
hennig at math.uni-hamburg.de, http://www.math.uni-hamburg.de/home/hennig/
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