Cubic Spline Interpolator

Tool for building splines based on pre-calculated (x, y) set of points.

Requirements

• python3.8+
• pip
• virtualenv (optional)

Pip packages

Install required packages using virtualenv

python -m virtualenv env && source env/bin/activate
python -m pip install -r requirements.txt

Usage

The script can be run as:

python main.py --options

The set of available options are:

• --range_start: left range boundary, default=-10.0, example: -7.5
• --range_end: right range boundary, default=10.0, example: 5.0
• --range_length: number of values in range, default=30000, example: 1000
• --intervals: number of intervals, default=10, example: 50
• --compare_default/--do_not_compare: compare custom spline with default scipy spline, default=False

Example

Set range [-10.0, 20.0] with 50 intervals

python main.py --range_end 20 --intervals 50

Output

Output contains:

• function
• first 8 pairs of arguments and function results
• first 8 pairs of arguments and interpolated values
• spline coefficients on each step
• interpolation error

Function arguments and results:

 x | -10.000 |  -9.999 |  -9.999 |  -9.998 |  -9.997 |  -9.997 |  -9.996 |  -9.995 |
------------------------------------------------------------------------------------
 y |  -0.054 |  -0.054 |  -0.054 |  -0.054 |  -0.054 |  -0.054 |  -0.054 |  -0.053 |

Spline arguments and interpolated values:

 x | -10.000 |  -9.999 |  -9.999 |  -9.998 |  -9.997 |  -9.997 |  -9.996 |  -9.995 |
------------------------------------------------------------------------------------
 y |  -0.054 |  -0.054 |  -0.054 |  -0.054 |  -0.053 |  -0.053 |  -0.053 |  -0.053 |

Coefficients on each step:

Step|    x    |    a    |    b    |    c    |    d    
------------------------------------------------------
  1 | -10.000 |  -0.054 |   0.000 |   0.000 |   0.000
  2 |  -7.778 |   0.126 |  -0.031 |  -0.152 |  -0.068
  3 |  -5.556 |  -0.116 |  -0.095 |   0.094 |   0.111
  4 |  -3.333 |  -0.052 |   0.172 |   0.146 |   0.023
  5 |  -1.111 |   0.446 |   0.167 |  -0.150 |  -0.133
  6 |   1.111 |   0.446 |  -0.167 |  -0.150 |  -0.000
  7 |   3.333 |  -0.052 |  -0.172 |   0.146 |   0.133
  8 |   5.556 |  -0.116 |   0.095 |   0.094 |  -0.023
  9 |   7.778 |   0.126 |   0.031 |  -0.152 |  -0.111
 10 |  10.000 |  -0.054 |  -0.137 |   0.000 |   0.068

Interpolation error: 0.11198

Plot

10 intervals

30 intervals