Large curly braces for ONLY SOME rows of an array?

Question

I'd like to use curly braces to demarcate parts of an equation. Right now I'm trying to do so using multirow. Is there a better way, ideally one that is compatible with automatic sizing?

\documentclass[11pt]{article}
\usepackage{amsmath,multirow}

\begin{document}

    \begin{equation}
    \begin{array}{r l l}
    y_{it} =    &   \alpha_i + v_i \times P_t & \multirow{4}{*}{\big\} parametric}\\
                        &   + \beta_1 \left( \text{SR}_t \times \text{log(LM)}_i\right)\\
                        &   + \beta_2 T_{it} + \beta_3 \left(T_{it} \times \text{SR}_i\right) + \beta_4 \left(T_{it} \times \text{log(LM)}_i\right) \\
                        &   + \beta_5 \left(T_{it} \times \text{SR}_t \times \text{log(LM)}_i\right) \\
                        &   + f_1\left(\text{F}_{it} \otimes \text{log(LM)}_i \times T_{it} \times SR_{t}\right) & \} nonparametric\\
                        &   + \delta_1^i \text{F}_{it} + \delta_2^i \left(T_{it} \times \text{F}_{it}\right)& \} random \\
    \end{array}
    \end{equation}

\end{document}

Answer 1

The following code borrows from How do I put a side brace around several lines in the align* environment?

% arara: pdflatex
% !arara: indent: {overwrite: yes}
\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{equation}
    \begin{array}{r@{\;}l}
        \setlength{\jot}{4.5pt}
        y_{it} & =       \alpha_i + v_i \times P_t                                                                                       \\[\jot]
               &
        \begin{array}{ll}
               & + \beta_1 \left( \text{SR}_t \times \text{log(LM)}_i\right)                                                             \\[\jot]
               & + \beta_2 T_{it} + \beta_3 \left(T_{it} \times \text{SR}_i\right) + \beta_4 \left(T_{it} \times \text{log(LM)}_i\right) \\[\jot]
    \end{array}
    \smash{\left.\begin{array}{@{}c@{}}\\[\jot]\\[\jot]\end{array}\right\}} \text{parametric}\\[\jot]
    &
    \begin{array}{ll}
          & + \beta_5 \left(T_{it} \times \text{SR}_t \times \text{log(LM)}_i\right)             \\[\jot]
          & + f_1\left(\text{F}_{it} \otimes \text{log(LM)}_i \times T_{it} \times SR_{t}\right) \\[\jot]
    \end{array}
    \smash{\left.\begin{array}{@{}c@{}}\\[\jot]\\[\jot]\end{array}\right\}} \text{non-parametric}\\[\jot]
    &
    + \delta_1^i \text{F}_{it} + \delta_2^i \left(T_{it} \times \text{F}_{it}\right)\}\text{random}
    \end{array}
\end{equation}
\end{document}

Answer 2

The blkarray package could be a solution. However it has some drawbacks, in particular, the array won't be centred and you'll have to make some manual adjustment. The curly braces are vertically aligned.

\documentclass[11pt]{book}
\usepackage[utf8]{inputenc}
\usepackage[showframe, nomarginpar, textwidth = 15cm]{geometry} 
\usepackage{amsmath}
\usepackage{blkarray}
\usepackage{nccmath}
\usepackage{blkarray} 

\begin{document}

\begin{equation}
\renewcommand{\arraystretch}{1.25}
\hspace{-6em} \begin{blockarray}{r l@{{} + {}} l}
y_{it} = & \alpha_i & v_i \times P_t\\
%
\begin{block}{r l@{{} + {}} l\Right{\}}{parametric}}
  & & \beta_1 \left(\text{SR}_t \times \log(\text{LM})_i\right)\\
  & & \beta_2 T_{it} + \beta_3 \left(T_{it} \times \text{SR}_i\right) + \beta_4 \left(T_{it} \times \log(\text{LM})_i\right) \\
\end{block}
%
& & \beta_5 \left(T_{it} \times \text{SR}_t \times \log(\text{LM})_i\right) \\
%
\begin{block}{r l@{{} + {}} l\Right{\}}{nonparametric}}
 & & f_1\left(\text{F}_{it} \otimes \log(\text{LM})_i \times T_{it} \times SR_{t}\right) \\
\end{block}
%
\begin{block}{r l@{{} + {}} l\Right{\}}{random}}
 & & \delta_1^i \text{F}_{it} + \delta_2^i \left(T_{it} \times \text{F}_{it}\right)\\
\end{block}
\end{blockarray}
\end{equation}

\end{document}