Curve Fitting and Plotting

[Ben Abbott]

On Sep 26, 2008, at 6:32 AM, Kearan Mc Pherson wrote:

> Hi
>
> I am new to Octave and Gnuplot. I need help on fitting a curve  
> through a data.dat file, that contains values x an y in column format.
> Any ideas where to start?
>
> Kind regards

If the data is in two columns, and you'd like a simple polynomial  
fit ...

## Load the data into (x,y)
data = load ('data.dat');
xdata = data(:,1);
ydata = data(:,2):

## Fit a 2nd order polynomial
order = 2;
p = polyfit (xdata, ydata, order);

## Evaluate the fitted polynomial
x = linspace (min(xdata), max(xdata), 101)
y = polyval (p, x);

## Plot
plot (x, y, '-' xdata, ydata, 's')
legend ('Fitted polynomial', 'Original Data')

Ben