Ternary plot on Cartesian coordinates

Does anyone know how to recreate a similar plot (overlapping the two plots into one) as below? Checked previous forums (link below) regarding this but I can't find a suitable answer. Thanks everyone!

https://uk.mathworks.com/matlabcentral/answers/321591-how-to-make-ternary-plots-in-matlab

[darova]

How to draw blue region?

[Phoenix]

Hello! I'm basically trying to draw a smilar plot with this one below; not necassrily the blue region as I have shown previously but the concept is similar. Thanks for your help!

[darova]

What about plot function?

Answer 1

[Pratheek Punchathody]

As per my understanding it is required to create a ternary plot. There is no option for performing a ternary plot from within the plot app in MATLAB.

However, here are a few file exchange submissions which I think you may find useful.

alchemyst/ternplot and Ternary Plots are two of the several submissions in MATLAB File Exchange on MATLAB Central which is a forum for our product users to interact, exchange information and knowledge, without MathWorks' involvement. Feel free to contact the author of this submission directly for specific questions about the implementation.

Hope this helps