Least Squares Quadratic Curve Fitting in C

The C program solves the standard least squares equation using Gauss-Jordan Elimination by getting the reduced row echelon form.

Test data has one feature and one label. It is inserted in runner.c as well as data.dat. Plots are generated using gnuplot and the script can be found in script.plt. The file 'LeastSquares.m' is a MATLAB implementation of the same idea.

The sample data is a quadratic fit, but the code can be slightly modified to fit any standard predefined equation.

Instructions

To execute the program as it is:

gcc runner.c -o runner
./runner

If you want to plot the equation:

gnuplot script.plt

(Obviously, you'll need gnuplot for this)

Sample Data

$$ w = ah^2 + bh + c $$

where w is the weight and h is the height.

Serial No	Height in cm	Weight in kg
1	160	68
2	155	78
3	143	56
4	162	70
5	170	72
6	175	78
7	167	68
8	163	54
9	156	43
10	172	71
11	180	65
12	159	59
13	169	63
14	157	62
15	161	90
16	171	45
17	181	62
18	177	57
19	140	80

Result

We get: a = 0.003703, b = -1.288406, c = 176.578090

Plot:

(The black dot shows the weight corresponding to predicted weight at 185 cm height)