The end result of what I'm doing is to create a trend line for a graph that shows how many records were created by week for a specified date range.

I've been able to create the summary fields and breaks to show a chart by week and cumulative. I know how to calculate a trend line. But the problem is coming up with a way to calculate this trend within the FileMaker realm.

The problem I'm having is finding out what the average is for each summary part. Each summary break is divided by week of the year and sorted by this number.

As far as creating a calculation/summary is concerned, how can I know which summary I'm currently on? I suppose I could script this as well, but how would I tell it to move/focus to the next summary?

I don't think I have managed to understand your description, so this is merely a guess:

how can I know which summary I'm currently on?

You are on the summary of the breakfield value of the current record.

how would I tell it to move/focus to the next summary?

If the current record is the first record of its group, you can move to (the first record of) the next group by:

Go to Record [ Get ( RecordNumber ) + GetSummary ( Table::sCount ; Table::Breakfield ) ]

where sCount is a summary field defined as count of ID.

I knew that trying to explain this would be a bit difficult. And understanding it would be even harder.

In a nutshell, I'm trying to create a linear trendline using the graph feature. I'm finding that it's not a easy as I thought.

In a nutshell, I'm trying to create a linear trendline using the graph feature.

Yes, that is the part that I did understand (sort of). However, a linear trendline can be calculated in several ways, and the graph feature does not calculate anything (well, except the curved line).

To do this inside Filemaker, you'd need to perform a linear regression in order to get the a and b parameters in y = ax + b. Next, you'd use that in order to calculate two x,y points at the opposite ends of your x range. Finally, you'd feed the resulting coordinates to the graph - and you'd only see the trendline, without the original scatter data.

I wonder if it's worth the bother.

While I can do the calculations like you suggested, it's not going to be worth my time be create a report that will be generated once a month. I'll just export the data into Excel and use their graphing capabilities.

I'm suspecting that FileMaker Inc. will improve the graphing capabilities with the next major release. I'll submit this feature to them.

Thanks for your time.