could you give me advice again?

I posted a few days ago about same question.

But I can't understand well and I think it is not accurate about "polyfitc" when I used it.

For example,

RNodes(2.8667)>>>Aero Twst(13.308), RNodes(2.8667)>>>chord(3.532)

I want to express such as upper.

it means that they are related mutually.

when I posted such as similiar question before, I got reommendation to use "polyfit"

But it was not accurate compared to original values when I graphed.

And I got another answer, but I coudln't understand well.

so Could you help me again ?

< I need to use original values without change a little>