Descriptor graphics in MATLAB: second horizontal axis

When studying the descriptor graphics in MATLAB, there was a shortage of "userfriends" of the functional, namely the absence of a standard command allowing to add an additional horizontal axis.
 
 
Adding an additional vertical axis, using the command. plotyy provided and in help to it, in the topics section, there is an example of adding an additional axis x , but this example, like the team itself, is not without flaws, which the developer himself graciously tells us:
plotyy is not recommended
the description of the command axes ;
 
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