[STATSGRASS] gstat - trend over 3th polinominal

[Jarek Jasiewicz]

Hi
I found that result of formula:

gs=gstat(id="x", formula=zinc~(x+y)^2, data=meuse)
pgs=predict(gs, newdata, meuse.grid)

is equvalent to:


gs=gstat(id="x", formula=zinc~x+y, data=meuse, degree=2)
pgs=predict(gs, newdata, meuse.grid)


so I tried:
gs=gstat(id="x", formula=zinc~(x+y)^4, data=meuse)
pgs=predict(gs, newdata, meuse.grid)

and it worked!

so it is possible to calculate trend over 3th polynominal (now its not a 
metter for what :))) in that way?

regards
Jarek