;
; sfit
deg=1
yfit=sfit(data,deg,/irreg,kx=kx,/max_degree)
;
; curvefit
;
parms=dblarr(3)
funcnm='fitplanefunc'
; a[0]*x + a[1]*y + a[2]*z + a[3]=0
; compute average pnt
;
a=size(data)
npnts=a[2]
pavg=total(data,2)/npnts
d=sqrt(pavg[0]^2 + pavg[1]^2 + pavg[2]^2)
;
; create vector pnts xmin to xmax
; ymin to ymax

a=min(data[0,*],iminx)
a=max(data[0,*],imaxx)
a=min(data[1,*],iminy)
a=max(data[1,*],imaxy)
;
vx=data[*,imaxx] - data[*,iminx]
vy=data[*,imaxy] - data[*,iminy]
vx=crossp(vx,vy)
parms=[vx[0],vx[1],d]/vx[2]
w=dblarr(2*npnts) + 1d
noderiv=1

yfitcf=curvefit(reform(data[0:1,*],2*npnts),reform(data[2,*],npnts),w,parms,chisq=chisq,/double,function_name=funcNm,$
		 noderiv=noderiv,status=status,yerror=yerror)

difcf=reform(data[2,*],npnts) - yfitcf