Sadly, Filemaker's graphing abilities are not great... you could try a scatter plot, with dates on the x-axis and readings on the y-axis (use delimited data i.e. lists, by selecting that from the 'data source' options)
I tend to like a return delimited list with rows for all dates, since I don't need another table.
But yes, you do have to fill in the gaps for the chart to work.
did you ever come up with a better solution than using a plugin?
If you have to create another table, how would I go about doing that?
I have records that are only a second apart sometimes.
would I create records for every second, then populate the records with my info?
I've tried looking for a forum post on this, without any luck.