I have to write some equations in latex, but I'm having trouble finishing them.
My Latex equation for image 1:
\widehat{f}(x,y)=median \left\{g(s,t)\right\}
My Latex equation for image 2:
A\oplus B = U A_{b}
How can I make a subscript below the formulas?
You want
\hat{f}(x,y) = \underset{(s,t)\in S_{xy}}{\mathrm{median}} \{g(s,t)\}
And
A \oplus B = \underset{b\in B}{\cup} A_b
The important things being:
\underset which takes two arguments, the first is put under the second.\mathrm to make median appear upright and differentiate it from a multiplication of 6 variables named m, e, d, i, a, and n.\{ and \} need backslashes because { and } are part of the LaTeX base language.\cup which is a nicer symbol for a union.
g(x,y)=\begin{cases}1 & \text{If $s$ hits $f$}\\ 0 & \text{otherwise}\end{cases} and requires the package amsmath
Aug 28, 2013 at 15:55
at least the first example is a case where limits are applied to an operator. using amsmath, put this in the preamble:
\DeclareMathOperator*{\median}{median}
and enter the math expression as
\[ \hat{f}(x,y)= \median_{(s,t)\in S_{xy}} \left\{g(s,t)\right\} \]
with this result:
\DeclareMathOperator will set the specified string as roman, although other alphabet styles can be specified; the starred version causes strings designated as sub- or superscripts to the operator to be set as limits.
for the second example, it's reasonable to treat this the same way, but specifying italic:
\DeclareMathOperator{\Uoperator}{\mathit{U}}
then ... \Uoperator_{b\in B} ... would yield the requested result.
\DeclareMathOperator* is designed to support limits on its argument -- but only in display mode. (Limits would appear to the side in text mode.) This does require amsmath. Since this doesn't work for you, please ask a separate question, providing a complete compilable example showing what you are doing, and cite this question and answer in yours, describing exactly what is different in what you are doing.
Feb 12, 2019 at 16:16
\documentclass{article} \usepackage{amsmath} \DeclareMathOperator*{\median}{median} \begin{document} \[ \hat{f}(x,y)= \median_{(s,t)\in S_{xy}} \left\{g(s,t)\right\} \] \end{document} works beautifully on my machine.
Uin the second example? I'd say it's\bigcup_{b\in B}