attempt to split up datasets by NAN value so different colors can be applied

[MoralCode]

this is some work i started for #409

i tried several different approaches and keep running into an issue where rust complains about returning owned values.

i dont know if there are ways around that but i wanted to put my code here in case someone more knowledgeable can see what im doing wrong

the general approach im going for take the same approach as https://github.com/MoralCode/TUI-coolors-demo (splitting the datasets up to apply different colors to each of them) since it seems like styling information is applied to an entire dataset at once.