# How to get a single left curly bracket that spans an array without a corresponding right closing curly bracket

I am trying to put an array inside a single left curly bracket

I can make it work when it is closed by a right curly bracket like so

\begingroup\Large
\begin{equation*}
y_{GxBxP|G[i,j,k|i]} = \left\{
\begin{array}{l} 1\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (0.0, 0.1)\\
2\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (0.1, 0.2)\\
3\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (0.2, 0.3)\\
\cdots\\
99\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (9.8, 9.9)\\
100\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (9.9, 10.0)\\
\end{array} \right\}
\end{equation*}
\endgroup


But when try to remove the closing curly bracket it doesn't work

\begingroup\Large
\begin{equation*}
y_{GxBxP|G[i,j,k|i]} = \left\{
\begin{array}{l} 1\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (0.0, 0.1)\\
2\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (0.1, 0.2)\\
3\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (0.2, 0.3)\\
\cdots\\
99\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (9.8, 9.9)\\
100\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (9.9, 10.0)\\
\end{array}
\end{equation*}
\endgroup


What am I doing wrong?

Each \left requires an accompanying \right, so you can't just remove it in hopes that it goes away. This is because the \left...\right construct is used to scale the (extensible) delimiters based on the contents within it. So, one without the other doesn't provide the delimiting range within which to scale.

So, what do you do if you don't want an opening or closing delimiter? Use \left. or \right.. Note that this inserts a small space (\nulldelimiterspace).

With that in mind, you're probably looking for

\documentclass{article}

\usepackage{amsmath}

\begin{document}

$y_{GxBxP|G[i,j,k|i]} = \left\{ \begin{array}{l} 1\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (0.0, 0.1) \\ 2\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (0.1, 0.2) \\ 3\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (0.2, 0.3) \\ \vdots \\ 99\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (9.8, 9.9) \\ 100\ \text{if} \ z_{GxBxP|G[i,j,k|i]} \in (9.9, 10.0) \end{array} \right.$

\end{document}


Although, cases already provides what you're looking for here:

\documentclass{article}

\usepackage{amsmath}

\begin{document}

$y_{GxBxP|G[i,j,k|i]} = \begin{cases} 1 & \text{if } z_{GxBxP|G[i,j,k|i]} \in (0.0, 0.1) \\ 2 & \text{if } z_{GxBxP|G[i,j,k|i]} \in (0.1, 0.2) \\ 3 & \text{if } z_{GxBxP|G[i,j,k|i]} \in (0.2, 0.3) \\ \vdots & \\ 99 & \text{if } z_{GxBxP|G[i,j,k|i]} \in (9.8, 9.9) \\ 100 & \text{if } z_{GxBxP|G[i,j,k|i]} \in (9.9, 10.0) \end{cases}$

\end{document}


Here's another option with some eqparbox alignment for the LHS of each condition:

\documentclass{article}

\usepackage{amsmath,eqparbox}

\begin{document}

$y_{GxBxP|G[i,j,k|i]} = \begin{cases} \eqmakebox[LHS][r]{ 1} & \text{if } z_{GxBxP|G[i,j,k|i]} \in (0.0, 0.1) \\ \eqmakebox[LHS][r]{ 2} & \text{if } z_{GxBxP|G[i,j,k|i]} \in (0.1, 0.2) \\ \eqmakebox[LHS][r]{ 3} & \text{if } z_{GxBxP|G[i,j,k|i]} \in (0.2, 0.3) \\ \eqmakebox[LHS][r]{\vdots} & \\ \eqmakebox[LHS][r]{ 99} & \text{if } z_{GxBxP|G[i,j,k|i]} \in (9.8, 9.9) \\ \eqmakebox[LHS][r]{100} & \text{if } z_{GxBxP|G[i,j,k|i]} \in (9.9, 10.0) \end{cases}$

\end{document}