What does the notation $g\colon X \to Y$ mean in this Wikipedia page, under the section "Problem statement (supervised version)"?
what does the notation $g\colon X\to Y$ mean?
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notation
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1I generally use $\rightarrowtail$ instead of $\to$ but that is no big deal. Something like $f:X\rightarrowtail Y:x\mapsto y$ would mean $f(x)=y$ such that $x\in X$ and $y\in Y$. – 2018-06-20
3 Answers
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It means that $g$ is a function which takes elements from $X$ as inputs and returns elements in $Y$ as outputs.
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0Well, sometimes this notation is used to describe a morphism in a category. And morphisms needs not to be functions (e.g. in the category $\mbox{Set}^{op}$ a morphism $g: X \to Y$ is a function $Y \to X$). Anyway this is not the case here. – 2011-05-01
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The $g$ function there is the mapping between instances to output labels. In other words, it is the correct association of events and their respective patterns. Presumably, the goal of supervised pattern recognition is to assign patterns to events in a way that best mirrors the truth (i.e. the $g$ function).
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It describes a function; a mapping from one set (X) to another (Y). For a more details see Set-builder notation