Curve fitting application it’s a free tool to construct a curve or mathematical formula that has the best fit to dataset (series of data points), using least square method.

HOW TO INPUT THE DATA :

x=1,2,3,4.    or x=-1,-3,0.5,1
y=1,2,3,4     or y=-1,-3,0.5,1

You can use as many x and y values as you want (input unlimited nuber of data), 
You can view your data by clicking onVIEW button, in order to choose the appropriate regression model from the list, then click CALC button to fidn the coefficens of the model as well as the Coefficents of Determination

if you want to fit your dataset to the following equations : Exponential, Power, Half life, Michaelis Mentent(Plateau), and Gaussian curves : you need to provide the app with x and y dataset then click on the corresponding button (for Power curve press Power fit button)  (linear regression graph, nonlinear regression, multiple linear regression, polynomial regression, quadratic regression calculator, regresión y correlación lineal, )

if you want to fit your dataset to Linear or Polynomial curve then you need to provide the app with the degree of the polynomial, for Linear curve then the degree is 1