I haven't seen this question asked yet, so I guess the solution is quite simple, but I haven't been able to find it.
I need to plot several groups of lines (each of about 10-15 lines) and display legend, but not for each of the lines seperately but only for each group.
Specificaly, I have groups of impact craters arranged by the age of the surface they are on. Each group has around20-30 craters and there are 4 groups, so I want the legend of the graph to have 4 entries, one for each group.
Can someone help me with this? Thank you in advance.