We are often presented with an image of a plot with no way to get the actual values (e.g. screenshot, book excerpt). In situations like this, we turn to a Plot Digitizer, like this one: http://plotdigitizer.sourceforge.net. The one linked runs in Java and produces a CSV file that Mathcad can read.
It would be very useful if Mathcad could adopt this functionality and digitize plot images into matrices or vectors for direct calculation, without having to tinker with third party software.