alignat incorrect spacing

Question

I am coming from this thread Have characters (subscripts) in equation mode occupy the same width to make my equation occupy the same width. The solution is to use alignat. Now I add in 2 more equations above and the spacing goes wild. How do I fix this ? Ive tried a bunch of random things but they all end up looking like garbage.

\documentclass{article}
\usepackage{tabularx}
\usepackage{booktabs}
\usepackage{graphicx}
\usepackage{amsmath}
\begin{document}
\begin{alignat}{4}
    \hat{y}{\Psi}^t &= \Psi(h^t\text{h}) \
    \hat{y}^t_{\Phi,s,i} &= \Phi([\hat{y}{\Psi}^t \odot m_s,x_i^t];\text{BPS}_i) \label{eq:doublenets} \
    \hat{y}^t &= \alpha^t{l,\text{h}}\hat{y}^t &&\odot m_l &&+ \mathop{\textstyle\sum_{i}} \alpha^t_{l,i}\hat{y}^t_{l,i} &&\odot (1 - m_l) \label{eq:update1} \
    \hat{y}^t &= \alpha^t_{r,\text{h}}\hat{y}^t &&\odot m_r &&+ \mathop{\textstyle\sum_{i}} \alpha^t_{r,i}\hat{y}^t_{r,i} &&\odot (1 - m_r) \label{eq:update2}
\end{alignat}
\end{document}

The problem is the places where you put (and do not put) the &. — mickep, Apr 25 '23 at 14:50
so what should i do ? i just want the 2 equations below to additonally align at \odot — Kong, Apr 25 '23 at 14:59

score 4 · Accepted Answer · answered Apr 25 '23 at 15:29

4

Just hide the width of the entries in the first rows, eg

\documentclass{article}
\usepackage{tabularx}
\usepackage{booktabs}
\usepackage{graphicx}
\usepackage{amsmath}
\begin{document}
\begin{alignat}{4}
    \hat{y}{\Psi}^t &= \Psi(h^t{\mathrm{h}})\hspace{-\textwidth} \
    \hat{y}^t_{\Phi,s,i} &= \Phi([\hat{y}{\Psi}^t \odot m_s,x_i^t];\mathrm{BPS}_i)\hspace{-\textwidth} \label{eq:doublenets} \
    \hat{y}^t &= \alpha^t{l,\mathrm{h}}\hat{y}^t &&\odot m_l &&+ \mathop{\textstyle\sum_{i}} \alpha^t_{l,i}\hat{y}^t_{l,i} &&\odot (1 - m_l) \label{eq:update1} \
    \hat{y}^t &= \alpha^t_{r,\mathrm{h}}\hat{y}^t &&\odot m_r &&+ \mathop{\textstyle\sum_{i}} \alpha^t_{r,i}\hat{y}^t_{r,i} &&\odot (1 - m_r) \label{eq:update2}
\end{alignat}
\end{document}

I also fixed \text which should not be used here, to \mathrm, I missed that last time.

answered Apr 25 '23 at 15:29

David Carlisle

757,742

Jeez, i would have never thought of that solution. Many thanks you are very kind. Latex is so unintuitive and is something I will never get better at especially since I only visit it once a year when writing up my work.... – Kong Apr 25 '23 at 17:45
@Kong I wouldn't say this was that latex-specific, alignat is just a table, you would see same in html or other tables if you put a large entry in column 2 that column gets wider in all rows, as your image showed. – David Carlisle Apr 25 '23 at 17:49
Why not use \rlap on the post-= segment of the second line? – barbara beeton Apr 25 '23 at 18:53
@barbarabeeton \rlap{$\displaystyle{} ...$} or \mathrlap{\displaystyle...} from mathtools would work but I thought hspace was simpler here – David Carlisle Apr 25 '23 at 19:25

score 2 · Answer 2 · answered Apr 25 '23 at 16:53

You can use IEEEeqnarray provided by the IEEEtrantools package.

\documentclass{article}
\usepackage{amsmath}
\usepackage{IEEEtrantools}
\newcommand{\hup}{\mathrm{h}}
\newcommand{\tsum}{\mathop{\textstyle\sum}\nolimits}
\begin{document}
\begin{IEEEeqnarray}{rLLLL}
\hat{y}^t &= \alpha^t_{l,\hup}\hat{y}^t &\odot m_l &+
  \tsum_{i} \alpha^t_{l,i}\hat{y}^t_{l,i} &\odot (1 - m_l) \
\hat{y}^t &= \alpha^t_{r,\hup}\hat{y}^t &\odot m_r &+
  \tsum_{i} \alpha^t_{r,i}\hat{y}^t_{r,i} &\odot (1 - m_r)
\end{IEEEeqnarray}
And another one
\begin{IEEEeqnarray}{rLLLL}
\hat{y}{\Psi}^t &= \Psi(h^t{\hup}) \
\hat{y}^t_{\Phi,s,i} &
  \IEEEeqnarraymulticol{4}{L}{=\Phi\bigl([\hat{y}{\Psi}^t \odot m_s,x_i^t];\mathrm{BPS}_i\bigr)}
\label{eq:doublenets} \
\hat{y}^t &= \alpha^t{l,\hup}\hat{y}^t &\odot m_l &+
  \tsum_{i} \alpha^t_{l,i}\hat{y}^t_{l,i} &\odot (1 - m_l)
  \label{eq:update1} \
\hat{y}^t &= \alpha^t_{r,\hup}\hat{y}^t &\odot m_r &+
  \tsum_{i} \alpha^t_{r,i}\hat{y}^t_{r,i} &\odot (1 - m_r)
  \label{eq:update2}
\end{IEEEeqnarray}
\end{document}

Note that \text{h} and \text{BPS} are wrong and \text should be \mathrm. I also provided a shorthand for the text style \sum.

The column type L means left alignment with an empty atom at the beginning, so the spacing around the initial binary or relation symbol is correct.

alignat incorrect spacing

2 Answers2