Why is the Geometric Mean being reported as NaN or ##ERROR##?

The Geometric Mean is defined only for positive values. A more detailed definition can be found on Wikipedia. That means that if there is single cell with a value of zero, or below zero, the Geometric Mean will be undefined. When this happens, later versions of FCS Express will display this statistic in one of 2 ways:

• n/a, which is seen within a statistics table, or,
• as the text string ##ERROR##, when the value is reported as a token outside of a statistics table.

With digital FCS 3.0 data, zero or negative values in your data can often happen as a result of compensation.

In this case, a workaround to have a valid geometric mean is to eliminate the negative values by gating on the positive values. You can then get a valid Geometric Mean on those positive values.

In earlier version of FCS Express, the Geometric Mean of a negative value was represented as a zero.