How to make a (ggplot) line plot with different color segments conditional on direction?

Your merge didn't work because you only had two colour variables, but three data values. Adding a third colour variable as padding seems to do the trick. Geom_line takes it's colour from the previous datapoint's value, so the last value of "value2" is not used.

I would just point out this related question. It's a real leap to go from this solution to solving your particular problem, but I'm posting this in case it might help.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.