Stephen Montgomery-Smith wrote:
On Monday, June 3, 2013 7:12:34 PM UTC-5, Sam math wrote:I have a multivariate polynomial and want to keep only up to a certain degree. I already know how to do this for the univariate case. For 1 variable, I'd do: R.<x> = PolynomialRing(QQ) f = x^4 + x^2 + x^3 + x + 1 f = f + O(x^3) print f #output would be 1 + x + x^2... which is what I want. How do I do this for a multivariate polynomial? It says O(.) is not defined... R.<x,y> = PolynomialRing(QQ) f = x^3*y^3 + x^2 * y^4 + x*y + x + y + 1 How can I chop this polynomial up to a certain degree of x and y? I.e. I want to keep up until the second degree of x only (regardless of y). I know one way I could go about this is to just redefine the polynomial by looping through the first few coefficients, but I'm looking for a more efficient/easier way. Thanks!I think what Sam Math wants to do is this: he has two multivariate polynomials f and g, lets say in x and y. What he wants to do is to multiply f*g, and then throw away all the terms of degree higher than, say, x^100, or even all terms of degree higher than x^100 and y^200. He doesn't necessarily want a beautiful solution. What he wants is an efficient solution. Maybe "looping through the first few coefficients" is the best way to go. But any better solutions would be greatly appreciated.
sage: f x^3*y^3 + x^2*y^4 + x*y + x + y + 1 sage: f.truncate(x,3) x^2*y^4 + x*y + x + y + 1 sage: f.truncate(x,3).truncate(y,3) x*y + x + y + 1 -leif -- () The ASCII Ribbon Campaign /\ Help Cure HTML E-Mail -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-support?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
