NTE wrote on 7 Dec 2005 07:06:06 -0800:

N This maybe a stupid question (I'm not a statistician or
N mathematician).

N I have data that looks like this:

N Na 0.032617
N Cl 0.0265
N Ca 0.000524
N K 0.005523
N Mg 0.0000823
N PO4 0.00031
N HCO3 0.001655

N I am plotting it with categorical values on the xaxis and
N the numerical value on the y axis. I am using a logarithmic
N scale for the y axis.

N I am getting the "Negative or zero values cannot be plotted
N correctly on log charts. Only positive values can be
N interpreted on a logarithmic scale" message, which I see
N from the newsgroup is common if there are zeros in the data.
N However, the data I am using does not appear to be zero to
N me. All the numbers are positive, even if they are small.

You rightly point out that negative numbers cannot be plotted
(since their logs are imaginary numbers ) and I also wonder what
is going on! I took your data and plotted it as a standard line
chart in Excel 2002. The result was not too bad just like that.
I switched the y-axis scale to logarithmic and that worked too.
Do you have some sort of formatting problem?

James Silverton.
Potomac, Maryland.