Hi! Thank you very much!
The answer was very useful, though I could not get the directly using the commands given.
The reasons being
(1) My document has data coordinates and not functions like sin, and cos.
(2) Data has x coordinates ranging from 1000.. and therefore constrained command did not give me curves.
(3)command 'discont' troubled me a lot. I am yet to find out what it did? It gave me good mind exercise when answers did not come.
(4) I appreciated MAPLE only once when it gave me a frank msg. The meaning of it was 'Donot give me y options, I know what to do?". I had to delete y = -4..4!
It was worth trying out your suggestions since I am exposed more to maple mind.
I also got a crisp suggestion from my close friend. I quote the same here
Quote, " then do exactly those three steps. Give each set of points a name such as d1, d2,...
Use the least-squared command four times, and give the resulting expressions the names c1,c2,...
Then, use the plot command plot([c1,c2,...],x=...)" unquote.
I followed this meticulously (not making mistakes, reading each alphabet, balancing parenthesis and curly braces..).
This also gave me several learnings about how agile we have to be while using MAPLE.
Finally I got the answer from him. I am attaching the doc link as well as doc below.
Thank you both