Ah, that's good! I tested this again and discovered that the scatterplot chart choice was below the icons displayed-- it's off the screen! And without scroll bars, there's no way of knowing that there's another choice there. (That's on an iPad; I'm soon going to check out Numbers on the Mac, too.)
However, I've discovered another major limitation for my work. It does NOT seem able to do what Excel calls line scatterplots or what others would call trend lines.
That is, you have a sequence of data ordered by non-consecutive years, e.g.,
1912 140
1922 195
1938 260
1945 480
What it seems to produce in such cases is a ranked sequence--by point 1, point 2, point 3, etc. with equal spacing. In other words, it can do a line chart, with even spacing between the x-axis years... which, of course, isn't what one has in that data! The x-axis points should differ by 10 years, then 16, and then 7.
It's the same problem in Excel if you simply select line chart rather than scatter plot for such data, the data aren't displayed properly (you actually need to choose the scatter plot with lines to show the trend line).
Much historical data takes that form... where there hasn't been annual data gathering, but rather intermittent surveys.
Any ideas, Papa G.?? (Or, anyone else?!!) I have again overlooked a choice in Numbers? Or, an obvious work around?
If my verbiage isn't clear, I can post two comparative graphs showing what I mean! Thanks for any and all input!