\documentclass[12pt,a4paper,notitlepage]{report}
\usepackage{amsmath}
\usepackage{array}
\usepackage{multirow}
\begin{document}
\[
\begin{array}{llll} \hline
& \multirow{2}{*}{\tilde{b}\leq b^{NG}} & \multicolumn{2}{c}{\tilde{b}>b^{NG}} \\ \cline{3-4}
& & b^{G} \leq \tilde{b} & b^{G}>\tilde{b} \\ \hline
b^{UL} & b^{NG} & \tilde{b} & b^{G} \\ \hline
\end{array}
\]
\end{document}
This is the error I get:
Package amsmath Error: \tilde allowed only in math mode.ng text
It tried at changing \tilde{b} to $\tilde{b}$ but it gave the same error. I do not understand why this is not working as I created a math environment for the array by using \[ and \].
\multirow
is typeset in text mode. It's only\multicolumn
that adjusts to math mode inarray
and text mode intabular
.