[R] Mixed model for count data?

[Chun (Jimmie) Ye]

Hi all,

I have a rather peculiar dataset that I'm not sure how to model
properly. This is data from an instrument that measures the size of
particles but instead of giving a continuous value, it generates a
"histogram" of the counts for a particular bin size. So the data looks
like this:

                              Condition 1
           Condition 2
Dimension  Rep1.A Rep1.B Rep2.A Rep2.B   Rep1.A Rep1.B Rep2.A Rep2.B
2                 5            6           7            8
40         35        33         31
2.1              7            8           4            5            30
        30        31         29
2.2              10          11         10          12          20
    18        21         20
2.3              50          45         44          39          5
      8         7           7
2.4              80          90         75          77          8
      10       3           5
2.5              30          22         31          35          10
      5        7           9
...
50               0            0            0            0           0
          1          0          0

There are two biological replicates and two technical replicates for
each of the conditions of interest. If these were continuous, I would
just fit a nested mixed model to the data. But instead, I have counts.
I was thinking that this might be suitable for modeling using a
multinomial response. I could also just compare the distribution using
a KS test but I'm not sure how to incorporate the replicate
information (except for averaging). Finally, I thought perhaps I could
estimate directly from the histogram the variance components from the
data. Any thoughts is greatly appreciated!

~Jimmie