DPlot

Exactly as you write -- a bubble plot is what I want. I changed my two-valued nominal variable (in the third column) into the numeral one and received the right plot.

Thank you for your recommendation (as well as for implementing the DPlot tool -- imho, it is one of really intelligently behaving ...

Having two groups (A and B) of points A(x,y) and B(x,y), with information describing a membership of each point's belonging into either A or B, I can create a standard scatter-plot. However, each point should be plotted with a color according to a point's membership: e.g., red for all A-points, blue ...