How to generate relation between two variables from the corresponding values or graph between the variables?

Consider two variables X,Y for a particular value of X we receive a value of Y. For several values if X the corresponding values of Y can be plotted in the graph. Is there any way by which we can establish a relation between X and Y or find a mathematical expression.

Answer 1

[Walter Roberson]

If you only have a finite number of corresponding datapoints, then there are an infinite number of relationships that can be constructed that fit exactly. There will not be any way to determine whether any of those infinite relations is more "correct" unless you already have information about the "form" of the relationship. And if there is potentially noise in the data, or numeric inaccuracies in the calculation of the datapoints, then the problem becomes even more difficult.

[siddhartha jain]

if i limit my data points within a range then all the relations will provide correct answers on the points which i have taken in consideration ignoring the intermediate results should be acceptable. so i can take any of the relation as long as it provides correct solution.