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

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 = | 0 3 6 0 0 |
     | 0 8 5 7 8 |
     | 2 7 1 8 0 |

              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,{0, 0, 2}), map(QQ,R,{3, 8, 7}), map(QQ,R,{6, 5, 1}),
     ------------------------------------------------------------------------
     map(QQ,R,{0, 7, 8}), map(QQ,R,{0, 8, 0})}

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

o4 = {6, 5, 1}

o4 : List
i5 : phi#2

o5 = map(QQ,R,{6, 5, 1})

o5 : RingMap QQ <--- R

Ways to use makeRingMaps :