fit_2d_spike

Parameters:
A(1) = peak intensity of spike
A(2) = FWHM of spike
A(3) = abscissa of spike
A(4) = ordinate of spike
A(5) = background level
A(6) = background Xslope
A(7) = background Yslope
Model:
MODEL(X,Y) = A1*P((XA3)/A2)*P((YA4)/A2) + A5 + A6*(XA3) + A7*(YA4)
where P(U) is the shape function.
SHAPE is the 1D shape of the spike, it can be "spline" to use a
cubic Bspline function, "gauss" to use a gaussian or any user
defined routine which has the following prototype:
func SHAPE(&p, &dp, u) {gg_fit_2d_spike(data)
p = f(u);
dp = f'(u);
}
where f(u) is a "bellshaped" function and f'(u) is
its derivative; f(u) should have
with the following properties:
f(0) = 1
f(0.5) = 0.5
f(u) = f(u) (i.e. f is symmetric)
f(u) >= 0 everywhere
f'(u)>0 for u<0, f'(0)=0, f'(u)<0 for u>0 (i.e. f is "bellshaped")
the 3 first properties are needed to properly define the FWHM (Full
Half Width at Half Maximum).
Background:
BG = nil/0 no background (BG = 0 everywhere)
BG = 1 uniform background
BG = 2 BG(x,y) = a() + a()*(xx0) + a()*(yy0)
Spike:
Support: */
interpreted function, defined at contrib/yeti_fit_2d_spike.i line 385
