next | previous | forward | backward | up | top | index | toc | Macaulay2 web site
Points :: makeRingMaps

makeRingMaps -- evaluation on points

Synopsis

Description

Giving the coordinates of a point in affine space is equivalent to giving a ring map from the polynomial ring to the ground field: evaluation at the point. Given a finite collection of points encoded as the columns of a matrix, this function returns a corresponding list of ring maps.
i1 : M = random(ZZ^3, ZZ^5)

o1 = | 4 8 2 9 5 |
     | 9 5 0 4 4 |
     | 3 9 3 7 2 |

              3        5
o1 : Matrix ZZ  <--- ZZ
i2 : R = QQ[x,y,z]

o2 = R

o2 : PolynomialRing
i3 : phi = makeRingMaps(M,R)

o3 = {map(QQ,R,{4, 9, 3}), map(QQ,R,{8, 5, 9}), map(QQ,R,{2, 0, 3}),
     ------------------------------------------------------------------------
     map(QQ,R,{9, 4, 7}), map(QQ,R,{5, 4, 2})}

o3 : List
i4 : apply (gens(R),r->phi#2 r)

o4 = {2, 0, 3}

o4 : List
i5 : phi#2

o5 = map(QQ,R,{2, 0, 3})

o5 : RingMap QQ <--- R

Ways to use makeRingMaps :