Re: Fitting data to a curve

*To*: mathgroup at smc.vnet.net*Subject*: [mg73303] Re: Fitting data to a curve*From*: "Ray Koopman" <koopman at sfu.ca>*Date*: Fri, 9 Feb 2007 23:45:57 -0500 (EST)*References*: <eqengu$4gj$1@smc.vnet.net>

On Feb 8, 12:37 am, Peter Jay Salzman <p... at dirac.org> wrote: > I have a table of {x,y} data and a function: > > a y^2 + b x y + c x + d y + e = x^2 > > I'd like to do a least fit to determine the constants a, b, c, d, and e. I > think the function I want is Fit[] or FindFit[], but I can't coax Mathematica to do > this. I'm not entirely sure what to do with that x^2 since it has no > coefficient. > > I've never used these functions before; how can I do this least squares fit? > > Thanks! In[1]:= <<Graphics`ImplicitPlot` In[2]:= SeedRandom[1]; data = Table[Random[],{30},{2}]; In[3]:= f = Fit[data/.{x_,y_}->{x,y,x^2},{1,x,y,x*y,y^2},{x,y}] Out[3]= -.0952586 + .887256*x - .128435*y + .354883*x*y - .141003*y^2 In[4]:= ImplicitPlot[f == x^2,{x,0,1},{y,0,1}, Frame->True, Prolog->{AbsolutePointSize[5], Point/@data}];