iKRdiagram: Create KR diagram

The KR diagram and the PI diagram are related plots, but they take different approaches. Whereas the PI diagram depicts response limits for a fixed structure for varying pressures (P) and impulses (I), the KR diagram illustrates response limits for fixed pressure and impulse for varying structural properties, such as stiffness (K) and resistance (R).

In KR plots, a structure is considered acceptable if its stiffness (K) and resistance(R) are above both the ductility and the rotation limit lines. On the other hand, in the PI diagram, a structure's response is deemed acceptable if both pressure (P) and impulse (I) are below the limit line.