Notation and Definitions
1) Capital Sigma Notation:
The summation over a collection X = {𝒙1, 𝒙2,...,𝒙n-1, 𝒙n} or over the attributes of a vector x = [𝒙(1), 𝒙(2),...,𝒙(m-1), 𝒙(m) ] is denoted like this:
2) Capital Pi Notation:
It denotes a product of elements in a collection or attributes of a vector:
3) Cardinality of Set:
The cardinality of a set is a measure of a set's size, meaning the number of elements in the set. It is denoted as |A|.
For instance, the set A = { 1 , 2 , 4 } then |A| = 3 since there are only three elements in set A such as 1,2 and 4.
Referenced The Hundred-Page Machine Learning Book - Andriy Burkov
