fit curve/regression line to image of graph scanned from external source

Hi!

I need some advice, or hope that someone can share their experience with a commercially available Excel Spreadsheet I am considering buying. This is the problem:

I would like to fit a curve to a graph I have available only as an image (i.e., scanned from a piece of paper, or available as a pdf).

Apparently there is software out there that claims to do this (even providing several options such as linear vs. logistic, etc.). It is called "Chart Trend Analysis" and is available here: http://www.business-spreadsheets.com...ns.asp?prod=45 .

I have no idea whether this vendor is reputable, or how well this software would work. Before I dish out $50, can somebody share their experience?

If you can think of any other way to extract such info from an image file (I am looking for a simple, linear relationship), I would much appreciate your thoughts! [For those interested: All I need to answer is: "based on these data points, if a linear relationship underlies this data, the correlation is ..."]

Thanks!

as

I can't say anything about your provider, but I used online plot digitizer ( splinecloud.com/features/plot-digitizing/ ) and was quite satisfied. You can easily export the obtained data to excel or python for further work