Homework Help: Plot help, Culobs Law

1. May 9, 2007

sc86

1. The problem statement, all variables and given/known data
Okay here is the deal, I have made a experiment, and now I have some probs, getting the right stuff from gnuplot.

If I isolate qQ in Culombs Law I get:qQ = F*4*Pi*e0*r^2:
Here e0 is the permittivity of free space
r is a constent, the distence between the charges.
If I plot F*4*Pi*e0*r^2 as a function of qQ, the slope of the linear function schuld be one, right?.
I have the folowing data:

qQ F*4*Pi*e0*r^2 delta g(x)

3.94e-15 2.129e-15 2.2e-16
2.28e-15 7.413e-16 8.1e-17
1.17e-15 3.177e-17 3.2e-17
7.38e-16 -3.601e-16 4.8e-17
4.31e-16 -6.248e-16 7.1e-17
3.08e-16 -7.307e-16 8.0e-17
2.46e-16 -8.261e-16 8.9e-17
1.85e-16 -9.002e-16 9.6e-17
1.23e-16 -9.320e-16 9.9e-17

So I want to fit them to a linear function. I load this plot command:
#Nu definere vi funktionen f(x) som er den vi vil fitte efter:
g(x)=h*x+b

fit g(x) "data.txt" via h,b

set xlabel "qQ [C^2]"

set ylabel "(F*4*Pi*e0*r^2) [C^2]"

set title "Kraftens afhængihed af afstanden mellem 'punkt ladningerne.'"

plot g(x), "data.txt" w e

And then i get a fine plot, but also this in my fit log:
Wed May 09 16:19:02 2007

#datapoints = 9
residuals are weighted equally (unit weight)

function used for fitting: g(x)
fitted parameters initialized with current variable values

Iteration 0
WSSR : 9 delta(WSSR)/WSSR : 0
delta(WSSR) : 0 limit for stopping : 1e-005
lambda : 0.707107

initial set of free parameter values

h = 1
b = 1

After 4 iterations the fit converged.
final sum of squares of residuals : 5.99386e-031
abs. change during last iteration : -2.37224e-019

Hmmmm.... Sum of squared residuals is zero. Can't compute errors.

Final set of parameters
=======================

h = 1
b = -1.20129e-015

I bellive the problem is here:
Hmmmm.... Sum of squared residuals is zero. Can't compute errors.

I want gnuplot to give me uncertenties on the free values h and b, but it docent.
And got no clue on how to fix it.
So what is the problem, anyone?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. May 9, 2007

sc86

And now I got the titek wrong :SS: