[R] density calculation

[Antje]

Hello,

I have another, more statistic related question.
I have several different measurements as an output of an image analysis process
(e.g. size, intensity, ... of objects of interests).
Now, I would like to quantify the difference for each parameter measured in a
special condition comparing to the measurement of a reference condition.
If I plot the density distribution (simply calling density(data) ), I can see
differences. But the parameters I'm measuring are not gaussian distributed for
sure, sometimes a logarithmic visualization of the histogram gives a better
idea of the distribution than a linear one.
I'm not very deep into statistics and I was wondering whether I can use the
"density" method at all, if yes: shall I be aware of how to set the parameters
of this function or is standard enough (I think especially for the "logaritmic"
data, it could be better to use other parameters... )
Does anybody know something about "posteriory pdf"?
And then, are there methods how to compare density functions and how to
quantify their difference?

Sorry for all these questions. I would be happy, if anybody could give me a
hint how to approach the problem and probably refer to some good ("easy" to
read) literature on this topic.

Have a nice evening!
Antje