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. 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.

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).

I guess one can think of these values as outliers and that is what I am trying to exclude.

There is ample evidence that such an approach is acceptable.

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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