how to connect coordinates?

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Ani Asoyan
Ani Asoyan on 26 May 2020
Commented: Walter Roberson on 19 Mar 2021
Hi...I have these values.
each value of x corresponds to more than one value of y.... I want to plot y against x so that on x will be on absciss and y will be on ordinates,,, but I can't do it with plot since I can't interpret it as a function. How can I do it? Thanks.
Walter Roberson
Walter Roberson on 19 Mar 2021
You would need to store the multiple solutions in a cell array, such as
x = [1,2,3,4]
y = {[-2,0], -4, [-3, 2], [52,21,23]}
If you did something like that, then you would have a chance -- but you would have to define which members of the previous set got connected to which members of the next. For example, we can guess that maybe the -4 is to be connected to both the -3 and 2, but then should the -3 be connected to all three of 52, 21, 23, or should it be only connected to 52 (the first) and then the 2 (second) gets connected to the 21 and all left-over values (23) ? Or should the -3 be connected to the 52 and 21 ("adjacent") with the 2 connected to the 21 and 23 ? Or should the -3 be connected to all three and the 2 be connected to all three?
I would suggest to you that polynomials always have the same number of roots, but that sometimes the roots are not real-valued, and that it might instead make the most sense to replace the complex-valued ones with nan leaving the structure intact. This would make the most sense if the roots are in a consistent order, following the same branch in each case. For example, if you use the explicit formula for a cubic then you can choose each of the three forms and plot them individually, whereas if you use roots() then there is the possibility that the values might not be in consistent order, as roots potentially sorts according to (for example) increasing absolute magnitude.

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