These are very useful links but the first one I had already read but seems too complex and I could not follow in terms of my requirement.
And the other 2 are not about the dotted line but are really useful!! I haven't seen them!
You can use dual axis graph so that it gives two marks card and you can format accordingly.
As you know, there is no straight method in doing Line chart, there is some work around in the blogs. Please going through in details and find the solutions. Even I learn from this blog.
If you can give us a sample data set, we can try to accomplish what your expecting.
here are screen shots I did from my end:
1.Steps: Drag Date in the Column and converted into Continuations
2.Drag Date into Page Shelf and applied below options
3. Drag Any measure into the rows
4. In the Page Shelf and try plan it will show you expected results like below.
This worked! But both the axis is dotted how do I make only 2017 (green) not 2018(blue) dotted?
You can't have that kind of option for now in the tableau. I think you can create an idea and post in the forum.
As per as I know this is not possible to achieve in tableau.