The r value is a common way to indicate a correlation value. Only functions have domain and range. A set is a collection of things usually numbers.
Eg using Quoras math markup if I write 23 and put it in math mode it comes out as 2 3 which is the way exponentiation is typically shown in mathematics.
The r value is a common way to indicate a correlation value. Math stands for M - Mental A - Abuse T - To H - Humans Now you get why math is so hard to understand. Common Symbols Used in Set Theory. R-Squared is a statistical measure of fit that indicates how much variation of a dependent variable is explained by the independent variable s in a regression model.