Line based heatmap / 2d histogram ?

I have a bunch of measurement data with hundreds of samples and clear convergence / trend in data, which can be seen when plotting all line graphs in one plot. I would like to visualize possible trend(s) with line based heatmap, but cannot find any built-in functions for that. Is there any?

I found this in stackoverflow, but its for python. Here is something similar what I'm trying to accomplish:

it would be nice to control radius of influence, linear/exponential influence, etc...