Make formulas start at the same point

Question

I would like to list a few formulas which I have done as following:

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{enumerate}
\item \textbf{Hommes and in 't Veld AR(1) model:}
    \begin{align}
        x_t = \frac{1}{R^*}(n_{1,t} \phi_1 + n_{2,t}\phi_2)x_{t-1} + \epsilon_t.
    \end{align}
\item \textbf{Weak trend following AR(2) model:}
    \begin{align}
        x_t = \frac{1}{R^*}((n_{1,t} \phi_1 + 1.4n_{2,t})x_{t-1} - 0.4n_{2,t}x_{t-2}) + \epsilon_t.
    \end{align}
\item \textbf{Strong trend following AR(2) model:}
    \begin{align}
        x_t = \frac{1}{R^*}((n_{1,t} \phi_1 + 2.3n_{2,t})x_{t-1} - 1.3n_{2,t}x_{t-2}) + \epsilon_t.
    \end{align}
\item \textbf{General trend following AR(2) model:}
    \begin{align}
        x_t = \frac{1}{R^*}((n_{1,t} \phi_1 + (1+\phi_3)n_{2,t})x_{t-1} - \phi_3n_{2,t}x_{t-2}) + \epsilon_t.
    \end{align}
\end{enumerate}
\end{document}

The problem is that I would like to let these x_t begin at the same point. Does anyone know how to achieve this?

Answer 1

You can make use of amsmath's \intertext. By default this will not allow page breaks within the align environment, but if necessary it can be made possible.

\documentclass{article}
\usepackage{amsmath}

\begin{document}
\begin{enumerate}
\item \textbf{Hommes and in 't Veld AR(1) model:}
    \begin{align}
        x_t &= \frac{1}{R^*}(n_{1,t} \phi_1 + n_{2,t}\phi_2)x_{t-1} + \epsilon_t.\\
\intertext{\item \textbf{Weak trend following AR(2) model:}}
        x_t &= \frac{1}{R^*}((n_{1,t} \phi_1 + 1.4n_{2,t})x_{t-1} - 0.4n_{2,t}x_{t-2}) + \epsilon_t.\\
\intertext{\item \textbf{Strong trend following AR(2) model:}}
        x_t &= \frac{1}{R^*}((n_{1,t} \phi_1 + 2.3n_{2,t})x_{t-1} - 1.3n_{2,t}x_{t-2}) + \epsilon_t.\\
\intertext{\item \textbf{General trend following AR(2) model:}}
        x_t &= \frac{1}{R^*}((n_{1,t} \phi_1 + (1+\phi_3)n_{2,t})x_{t-1} - \phi_3n_{2,t}x_{t-2}) + \epsilon_t.
    \end{align}
\end{enumerate}
\end{document}

Answer 2

In this specific example you can also use aligned where I have defined the \Indent macro to allow you to control the indentation:

Notes:

• As hooy commented, With this method you do not get the equation numbers.

Code:

\documentclass{article}
\usepackage{amsmath}

\newcommand*{\Indent}{\par\hspace*{1.0cm}}

\begin{document}

\begin{enumerate}
\item \textbf{Hommes and in 't Veld AR(1) model:}
    \Indent$\begin{aligned}
        x_t = \frac{1}{R^*}(n_{1,t} \phi_1 + n_{2,t}\phi_2)x_{t-1} + \epsilon_t.
    \end{aligned}$
\item \textbf{Weak trend following AR(2) model:}
    \Indent$\begin{aligned}
        x_t = \frac{1}{R^*}((n_{1,t} \phi_1 + 1.4n_{2,t})x_{t-1} - 0.4n_{2,t}x_{t-2}) + \epsilon_t.
    \end{aligned}$
\item \textbf{Strong trend following AR(2) model:}
    \Indent$\begin{aligned}
        x_t = \frac{1}{R^*}((n_{1,t} \phi_1 + 2.3n_{2,t})x_{t-1} - 1.3n_{2,t}x_{t-2}) + \epsilon_t.
    \end{aligned}$
\item \textbf{General trend following AR(2) model:}
    \Indent$\begin{aligned}
        x_t = \frac{1}{R^*}((n_{1,t} \phi_1 + (1+\phi_3)n_{2,t})x_{t-1} - \phi_3n_{2,t}x_{t-2}) + \epsilon_t.
    \end{aligned}$
\end{enumerate}
\end{document}