Get graph and trendline to not display non-numerical values as zero

[SerenityNetworks]

I have a graph that draws information from two columns in a simple table. The information is drawn from cells that contains formulas, for example: =IF(COUNTA(F4:H4)>0,LN(E4),"-"). I've tried replacing the "-" with "", "x", and nothing, but the graph always picks up the non-numerical value and adjusts the trendline as if the values were zero. However, if I go to the table and manually delete the formulas from all the cells that do not contain numerical values then the graph's trendline displays correctly. Obviously, I want to leave the formulas in all the cells and still have the graph display as it would as if the non-numerical results were ignored. How can I either modify the formula or the graph to display without considering the non-numerical values in the source table?

Here is a link to a sample workbook that demonstrates the issue I'm having. The illustration below details the issue, if downloading the workbook sample is not an option.

Thank you in advance,
Andrew

 

[SerenityNetworks]

Ah, I just tried the NA() method. The error value kills other calculations dependent on the data in those columns. I might just duplicate the columns and use the "-" or similar, then just graph off one set of columns and calculate of the other set. I don't have time to work on it now. I just wanted to point out that the NA() method does have some disadvantages other than cosmetic.