Cubic Spline Inerpolation

Task

Implement cubic spline interpolation algorithm and draw resulting a graph for a given set of 2-dimensional points

Input file format

Any text file with 2N integer or floating point values. It must not contain any other data.
If the number of points is less than 3 or if there are at least 2 points with the same X coordinate the program will show an error messagebox.

Example:

-87.6083  32.7009
66.8744   42.2585
75.6633   44.6086
-55.5066  28.8486
46.2896   -12.5529
-51.2362  21.5556
78.5095   6.7208
95.6425   29.2169
-71.4888  -7.3083
-84.2601  9.0064

Screenshots

Plot constructed using the sample file (points.txt)
On the left there’s result of some online tool and the output of my program is on the right.

Project structure

|-- LICENSE                         
|-- README.md                       
|-- points.txt                      - Sample file with points
`-- src                             - Directory with source code
    |-- interpolation.cpp           - Logic for reading data and interpolating
    |-- interpolation.h             
    |-- main.cpp                    
    |-- mainwindow.cpp              - View logic
    |-- mainwindow.h                
    |-- mainwindow.ui               - Form
    |-- polynomial.cpp              - Class Polynomial
    |-- polynomial.h                
    |-- qcustomplot.cpp             - Library for plotting
    |-- qcustomplot.h               - Library for plotting
    `-- spline-interpolation.pro    - Qt project file