How to identify quadrants for points of a graph with boundary conditions?

[pv33]

I tried using the if statement but its not working 100%. so I calculated two values of d* and Ry and plotted a graph. I added the boundary conditions to the graph as Ry=1, D*=ry, d*=-ryln(ry), d=sqrt(3.14/2*ry). This gave me lines and divided the graph into 4 quadrants. The graph is in log scale. I name each quadrant as regime 1 ,2 ,3 ,4


Now since these points fall all over the graph I am trying to write something that will tell me which regime that point belongs to. I tried using if statement but I am making some mistake as eventhough points are in regime 2 and 4 I only get 1 or 3. my logical reasoning is not correct and would like some help if possible


Thank you

 

[Fluff]

Cross posted How to identify quadrants for points of a graph with boundary conditions?

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