[Octave-bug-tracker] [bug #34119] plotyy more restrictive that plot

[anonymous]

Follow-up Comment #10, bug #34119 (project octave):

No, the untested suggestion posted in #5 does not produce the output you
imagined it would. 


# test ability to plot three lines on plotyy() graph

x=y=y2=[1:10];
y3=[6:15];
plotyy(x,y,x,y2);
hold on
plot(x,y3);
hold off


The third line is plotted on the scale of y2 axis but is coloured to indicate
it relates to y1 axis. Output is invalid.

Yet again this shows that plotyy() is a hack. This sort of ad hoc . bolt-on
solution with unseen, undocumented affects on what axis is "current" etc will
be a constant cause of bugs, dysfunction and confusion. 

I already suggested that this functionality could probably be incorporated
into the existing plot() by simple addition of an option 'axes'
=[x1y1,x2y2,x1y2,,x2y1] 

This is already available in gnuplot and would require minimal coding to
implement. 

plot could then return three (or more) args as per plotyy() and remain
compatible with existing code expecting one return arg. 


from man plot:

  Here are some plot examples:

          plot (x, y, "@12", x, y2, x, y3, "4", x, y4, "+")


So apparently plot() can already parse an undetermined number of x,y plots
with options interspersed. 

This would get around all the (undocumented) special cases that occur with the
implicit "current axis" paradigm and probably reduce the size of the code
base. 

The true x2axis could go at the top and actually be a useful feature. 

ylabel() and friends could take an explicit optional second arg if they need
to be directed to y2axis etc. 


The resulting code would probably be simple and easier to maintain (and
hopefully document!). 


I am fully aware that the current mindset in the project is refractory to
outside suggestions (most open source project are run by defensive cliques)
but at least this possible solution is logged in the system should anyone wish
to fix this mess at some later time.

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