Hallo

I have the following problem.

I have nine points (x,y,z) and I want to fit a surface through them. I have the forumla for it.

So far I've tried:

I have a .txt file with the nine points. Then I creat a input file with the following content.

"

a_0=1.0

a_1=1.0

c_0=1.0

b_0=1.0

b_1=1.0

c_1=1.0

set xrange [0:60]

set yrange [0:60]

f(x,y)=(x^2)*(a_0+a_1*(y-c_0)^2)+b_0+b_1*(y-c_1)^4

fit 'test.dat' f(x,y) via a_0,a_1,b_0,b_1,c_0,c_1

splot f(x,y), 'test.dat' w p

"

(I know ^ is wrong. But with ** it is displayed uncorrectly)

If I want to plot it it says

load 'input.txt'

"input.txt", line 10: undefined variable: x

I also tried it with the variables u and v.

What am I doing wrong?

Thank you for you help.

Yours scincerely

Fabian