In a workbook with multiple charts on multiple spreadsheets, the chart option
to add a trendline is available on some of the charts and not on others -
why? (I have tried right clicking on the series - that is not the problem).
The data on the underlying spreadsheet appears to be entered and formatted
the same way. Of course, I have tried clicking on both axes, clicking on the
chart, off the chart, on the series line, on the series label in the legend
and so on. Yet, on other spreadsheets the feature works fine. I have tried
this on two PCs, with the same document (and the same errors) - in other
words, I doubt if re-booting will fix it either.