Tengo problemas para colocar los diferentes elementos de la siguiente imagen tikz en las posiciones correctas. Creo que el problema surge porque el ancho de los elementos dentro de la matriz difiere.
\documentclass[10pt]{article}
\usepackage[margin=0.75in]{geometry}
\usepackage{tikz}
\usetikzlibrary{matrix,decorations.pathreplacing,calc,graphs,decorations.markings,intersections,positioning}
\usepackage{mathtools}
\usepackage{amsmath}
\usepackage{amsthm} %for proof
\begin{document}
\[X=
\begin{tikzpicture}[baseline=-0.5ex]
\matrix [matrix of math nodes,left delimiter=(,right delimiter=),row sep=1cm,column sep=1cm] (m) {
0&\frac{p^{I}_{1S}.F^{-1}_{1S}(y^{f}_{2S}+y^{I}_{2S})}{p^{f}_{2S}.y^{f}_{2S}+p^{I}_{2S}.y^{I}_{2S}}&0&0 \\
\frac{p^{I}_{2S}.F^{-1}_{2S}(y^{f}_{1S}+y^{I}_{1S})}{p^{f}_{1S}.y^{f}_{1S}+p^{I}_{1S}.y^{I}_{1S}}&0&0&0 \\
0&0&0&\frac{p^{I}_{1L}.F^{-1}_{1L}(y^{f}_{2L}+y^{I}_{2L})}{p^{f}_{2L}.y^{f}_{2L}+p^{I}_{2L}.y^{I}_{2L}} \\
0&0&\frac{p^{I}_{1L}.F^{-1}_{1L}(y^{f}_{2L}+y^{I}_{2L})}{p^{f}_{2L}.y^{f}_{2L}+p^{I}_{2L}.y^{I}_{2L}}&0 \\};
\draw[dashed] ($0.5*(m-1-2.north east)+0.5*(m-1-3.north west)$) --
($0.5*(m-4-2.south east)+0.5*(m-4-3.south west)$);
\draw[dashed] ($0.5*(m-2-1.south west)+0.5*(m-3-1.north west)$) --
($0.5*(m-2-4.south east)+0.5*(m-3-4.north east)$);
\node[above=12pt of m-1-1] (top-1) {1};
\node[above=12pt of m-1-2] (top-2) {2};
\node[above=12pt of m-1-3] (top-3) {1};
\node[above=12pt of m-1-4] (top-4) {2};
\node[left=12pt of m-1-1] (left-1) {1};
\node[left=12pt of m-2-1] (left-2) {2};
\node[left=12pt of m-3-1] (left-3) {1};
\node[left=12pt of m-4-1] (left-4) {2};
\node[rectangle,above delimiter=\{] (del-top-1) at ($0.5*(top-1.south) +0.5*(top-2.south)$) {\tikz{\path (top-1.south west) rectangle (top-2.north east);}};
\node[above=10pt] at (del-top-1.north) {$S$};
\node[rectangle,above delimiter=\{] (del-top-2) at ($0.5*(top-3.south) +0.5*(top-4.south)$) {\tikz{\path (top-3.south west) rectangle (top-4.north east);}};
\node[above=10pt] at (del-top-2.north) {$L$};
\node[rectangle,left delimiter=\{] (del-left-1) at ($0.5*(left-1.east) +0.5*(left-2.east)$) {\tikz{\path (left-1.north east) rectangle (left-2.south west);}};
\node[left=10pt] at (del-left-1.west) {$S$};
\node[rectangle,left delimiter=\{] (del-left-2) at ($0.5*(left-3.east) +0.5*(left-4.east)$) {\tikz{\path (left-3.north east) rectangle (left-4.south west);}};
\node[left=10pt] at (del-left-2.west) {$L$};
\end{tikzpicture}
\]
\end{document}
Respuesta1
Algo como esto. Debe definir el tamaño del nodo como tal en la opción.
nodes={anchor=center,minimum width=3cm,minimum height=2cm}
Código
\documentclass[10pt]{article}
\usepackage[margin=0.75in]{geometry}
\usepackage{tikz}
\usetikzlibrary{matrix,decorations.pathreplacing,calc,graphs,decorations.markings,intersections,positioning}
\usepackage{mathtools}
\usepackage{amsmath}
\usepackage{amsthm} %for proof
\begin{document}
\[X=
\begin{tikzpicture}[baseline=-0.5ex]
\matrix [matrix of math nodes,left delimiter=(,right delimiter=),row sep=1cm,column sep=1cm,
nodes={anchor=center,minimum width=3cm,minimum height=2cm}
] (m) {
0&\frac{p^{I}_{1S}.F^{-1}_{1S}(y^{f}_{2S}+y^{I}_{2S})}{p^{f}_{2S}.y^{f}_{2S}+p^{I}_{2S}.y^{I}_{2S}}&0&0 \\
\frac{p^{I}_{2S}.F^{-1}_{2S}(y^{f}_{1S}+y^{I}_{1S})}{p^{f}_{1S}.y^{f}_{1S}+p^{I}_{1S}.y^{I}_{1S}}&0&0&0 \\
0&0&0&\frac{p^{I}_{1L}.F^{-1}_{1L}(y^{f}_{2L}+y^{I}_{2L})}{p^{f}_{2L}.y^{f}_{2L}+p^{I}_{2L}.y^{I}_{2L}} \\
0&0&\frac{p^{I}_{1L}.F^{-1}_{1L}(y^{f}_{2L}+y^{I}_{2L})}{p^{f}_{2L}.y^{f}_{2L}+p^{I}_{2L}.y^{I}_{2L}}&0 \\};
\draw[dashed] ($0.5*(m-1-2.north east)+0.5*(m-1-3.north west)$) --
($0.5*(m-4-2.south east)+0.5*(m-4-3.south west)$);
\draw[dashed] ($0.5*(m-2-1.south west)+0.5*(m-3-1.north west)$) --
($0.5*(m-2-4.south east)+0.5*(m-3-4.north east)$);
\node[above=12pt of m-1-1] (top-1) {1};
\node[above=12pt of m-1-2] (top-2) {2};
\node[above=12pt of m-1-3] (top-3) {1};
\node[above=12pt of m-1-4] (top-4) {2};
\node[left=12pt of m-1-1] (left-1) {1};
\node[left=12pt of m-2-1] (left-2) {2};
\node[left=12pt of m-3-1] (left-3) {1};
\node[left=12pt of m-4-1] (left-4) {2};
\node[yshift=-2cm,rectangle,above delimiter=\{] (del-top-1) at ($0.5*(top-1.south) +0.5*(top-2.south)$) {\tikz{\path (top-1.south west) rectangle (top-2.north east);}};
\node[above=10pt] at (del-top-1.north) {$S$};
\node[yshift=-2cm,rectangle,above delimiter=\{] (del-top-2) at ($0.5*(top-3.south) +0.5*(top-4.south)$) {\tikz{\path (top-3.south west) rectangle (top-4.north east);}};
\node[above=10pt] at (del-top-2.north) {$L$};
\node[rectangle,left delimiter=\{] (del-left-1) at ($0.5*(left-1.east) +0.5*(left-2.east)$) {\tikz{\path (left-1.north east) rectangle (left-2.south west);}};
\node[left=10pt] at (del-left-1.west) {$S$};
\node[rectangle,left delimiter=\{] (del-left-2) at ($0.5*(left-3.east) +0.5*(left-4.east)$) {\tikz{\path (left-3.north east) rectangle (left-4.south west);}};
\node[left=10pt] at (del-left-2.west) {$L$};
\end{tikzpicture}
\]
\end{document}