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Mathematical Relations. Dr. Ron Smith Graceland University. Me. Father. Daughter. Widow. Mathematical relations. We can draw a picture to illustrate a relation between members of a set. Me. Father. Daughter. Widow. Mathematical Relations. Spouse. Me. Father. Daughter. Widow.
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Mathematical Relations Dr. Ron Smith Graceland University
Me Father Daughter Widow Mathematical relations • We can draw a picture to illustrate a relation between members of a set.
Me Father Daughter Widow Mathematical Relations • Spouse
Me Father Daughter Widow Mathematical Relations • This is a directed graph (digraph). • Dots are vertices, arrows are edges.
Me Father Daughter Widow Mathematical Relations • Birth Parent
Mathematical relations • A step parent is the spouse of a birth parent. • A parent is either a birth parent or a step parent. • A grandparent is a parent of a parent. • We combine these simpler relations to get the complex relation “Grandparent”
M F W D Me Father M F W D S = Daughter Widow Adjacency Matrices • Construct an adjacency matrix for “Spouse”. 0 0 1 0 0 0 0 1 1 0 0 0 0 1 0 0
M F W D Me Father M F W D B = Daughter Widow Adjacency Matrices • “Birth Parent” 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0
Adjacency Matrices • To combine “Spouse” and “Birth Parent” to get “Step Parent” we simply multiply the adjacency matrices! • To combine “Birth Parent” or “Step Parent” to get “Parent” we add the adjacency matrices.
Spouse OF Birth Parent 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 1 1 0 0 0 0 0 0 0 Me Father 1 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 Daughter Widow A step parent is the spouse of a birth parent Step Parent!
Birth Parent Step Parent OR 0 0 0 0 0 0 0 1 0 0 0 1 1 0 0 0 0 0 0 0 1 0 0 0 Me Father 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 1 0 0 0 Daughter Widow A parent is a birth parent OR a step parent Parent!
Technical Note • We need to use computer logic instead of arithmetic • x AND y = 1 if x and y are both 1, and 0 otherwise. • We use • to stand for AND 1•1= 1 0•1= 0 1•0= 0 0•0= 0
Technical Note • x OR y is 1 if either x or y (or both) is 1, and 0 otherwise. • We use + to stand for OR 1+1= 1 0+1= 1 1+0= 1 0+0= 0
Technical Note • In fact, the logical operations AND and OR work exactly like multiplication and addition except for the fact that 1+1=1 instead of 2. • If we do matrix operations using AND and OR on adjacency matrices, we get the adjacency matrix of the combined relation!
Parent OF Parent 0 0 0 1 0 0 0 1 1 0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 Me Father 0 0 0 1 0 0 0 1 1 0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 Daughter Widow A grandparent is a parent of a parent Grandparent!
I’m my own Grandpa! I’m my own Grandpa, And my daughter’s her own Grandma, It seems funny, I know, but I Mathematically show-- that I’m my own Grandpa!