Oh dear oh dear!!! another arrogant statistician/scientist
One asks for help and instead one gets an ear full!!!
So much for the much vaunted helpful R community.
But thanks anyway, I guess you were trying........
Steve
On 2010/12/13 08:17 PM, Bert Gunter wrote:
Inline below. -- Bert
On Mon, Dec 13, 2010 at 9:42 AM, Steve Sidney<sbsid...@mweb.co.za> wrote:
Thanks for the questions.
1) The data represents micro-organism counts and a count of zero in this
case is highly unlikely given the info we have; including the other
participants.
?? Censoring or an experimental failure? Big difference.
2) The data is submitted in duplicate and then a standardised sum and
difference is established and is used to calculate a Z-score which is used
as a measure of performance.
Z scores are usually inappropriate for count data, which are discrete
and tend to be skew.
Given both 1) and 2) it is necessary to exclude a raw count of zero (since
the log of 0 is meaningless) and a count of one (since the log of 1 of
course is zero).
False. Correct statement is: "Because I do not know the statistical
methodology necessary to handle such discrete data with 0 counts, I
exclude them." You are confusing your ignorance of statistical
methodology with the need for spurious ad hoc treatments. 0 counts can
and should be handled by appropriate statistical methods (e.g.
possibly 0 inflated Poisson models via glm() or otherwise).
I guess one can think of these values as outliers and that is what I am
trying to exclude.
This is a wholly unscientific statement, I'm afraid.
There is ample evidence that such an approach is acceptable.
What evidence, pray tell? -- a prior culture of inappropriate
analyses, perhaps? I do not wish to engage in a debate about this,
but, again, all I can say is that the above statement is not
scientific. If I were consulting with you, I would say "Please show me
your 'evidence.' " But, of course, I am not, and won't.
None of this is to say that you aren't correct in all respects. It is
just that you have raised all my usual warning flags, so that I am
somewhat skeptical. But that's MY problem. This is the last I will say
on the matter, so feel free to get in the final word, as I will not
respond.
And I wish you success in your efforts.
-- Bert
Thanks for the interest
Steve
On 2010/12/13 06:47 PM, Stavros Macrakis wrote:
If you need to take the log of the values for your calculation, then
what does it mean that you have 0 values in the input?
And why do you need to exclude the 1 values?
Are you sure that a) you are doing the correct kind of analysis and b)
the analysis is correct if you exclude 0 and 1?
-s
On Mon, Dec 13, 2010 at 10:38, Steve Sidney<sbsid...@mweb.co.za> wrote:
Dear list
I have quite a small data set in which I need to have the following
values
ignored - not used when performing an analysis but they need to be
included
later in the report that I write.
Can anyone help with a suggestion as to how this can be accomplished
Values to be ignored
0 - zero and 1 this is in addition to NA (null)
The reason is that I need to use the log10 of the values when performing
the
calculation.
Currently I hand massage the data set, about a 100 values, of which less
than 5 to 10 are in this category.
The NA values are NOT the problem
What I was hoping was that I did not have to use a series of if and
ifelse
statements. Perhaps there is a more elegant solution.
Any ideas would be welcomed.
Regards
Steve
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