I will describe my problem in more detail. Thanks Naomi for your
comments. Below you'll fin the R script, output and info about my
experiment. I hope someone help me to figure out the problems.
I have two sampling time points, morning and afternoon, and twelve
different samples (let's say different tissues), so I have 2*12=24
MAs. The samples are neither biological nor technical replicates, they
are as I wrote already different samples.
My object is a data matrix of the kind "ExpressionSet", meaning I have
normalized intensity values (of course no negative values in the data
#With this pattern I hope to find DE genes between AM and PM time
points in #condition sample one. As I understand "1,1" is the NULL
expression pattern, #while "1,2" counts for ? AM different from ? PM,
Collection of 2 patterns
Pattern 1 has 1 group
Group 1: 1 13
Pattern 2 has 2 groups
Group 1: 1
Group 2: 13
> gg_data.out<-emfit(data,family="GG",hypotheses=pattern, num.iter=20)
EB model fit
Family: GG ( Gamma-Gamma )
Model parameter estimates:
alpha alpha0 nu
Cluster 1 357.0943 4.742546 0.05231341
Estimated mixing proportions:
Cluster 1 0.9838123 0.01618772
> gg.post.out<-postprob(gg_data.out, data)$pattern
I get the same result for other patterns or using not GG but LNN.
To test if a less complex dataset would work better, I used another
time course. The experiment is a time course of 6 MAs, two genotypes
(mutant and wild type) sampled at 0, 12 and 48 h after treatment. The
results are identical, NULL for posterior probability.
I have tried to contact M. Yuan and C. Kendziorski, but got no answers
to my mails.
If anyone can point me to the mistake or mistakes I am doing, or can
suggest another program available for R or standalone to analyse time
series without replicates, I will be very, VERY grateful.
Judith Lucia Gomez, PhD
BioPhysics and Molecular Plant Biology
Quoting Naomi Altman <naomi at="" stat.psu.edu="">:
> p.s. You need to post your code and sessionInfo to get help.
> At 05:08 AM 4/8/2011, you wrote:
>> Dear List,
>> I would like to use EBarrays to analyse 24 MAs without replicates.
>> have 12 samples taken at one time point, and 12 taken at other time
>> point. I want to find the genes differentially express at one time
>> point vs. the other.
>> I have chosen EBarrays because I don't have replicates. Until the
>> fitting of the model (emfit) it seems to work. However, when I want
>> check the post. probabilities I get NULL. I have tried all kinds of
>> things I could think of. The answer is always:
>> if I understand right, most genes belong to the ?1=?2 pattern
>> Pattern.1 Pattern.2
>> Cluster 1 0.9838123 0.01618766
>> But no matter how I set the pattern (including all MAs, comparisons
>> only one time point at a time, etc), the answer is always NULL for
>> post. prob.
>> Does anyone has any idea how to set my analysis, or at the very
>> why the calculation of post. probs always renders NULL?.
>> Thanks in advance.
>> Judith Lucia Gomez, PhD
>> Universit?t Potsdam
>> BioPhysics and Molecular Plant Biology
>> D-14476 Potsdam
>> Bioconductor mailing list
>> Bioconductor at r-project.org
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