Math & Science ⇒ equation term alignment bypassing leading sign

[abalenkm]

Dear LaTeX community,

I would like to align the equation terms to the left inside a "{pmatrix*}[l]" environment, but at the same time bypass the leading minus sign of selected terms:

original equation:

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(E_1 - E_2)/\dx - (E_3 - E_4)/\dy - \Jscr

normal {pmatrix*}[l] result:

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(E1 - E2)/dx
- (E3 - E4)/dy
- Jsrc

desired {pmatrix*}[l] result:

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  (E1 - E2)/dx
 - (E3 - E4)/dy
 - Jsrc

Any help will be greatly appreciated. Thank you.

[abalenkm]

I found an answer. This is achieved with a \phantom{} command that takes the width of a given parameter, i.e. in the example above to insert a phantom minus write:

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\phantom{-}(E_1 - E_2)/\dx
- (E_3 - E_4)/\dy
- \Jsrc

to obtain the desired result:

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  (E1 - E2)/dx
- (E3 - E4)/dy
- Jsrc

You may also wish to create a custom shortcut for a \phantom command to enable a faster access to this feature:

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\newcommand{\p}[1]{\phantom{#1}}

\p{-}(E_1 - E_2)/\dx
- (E_3 - E_4)/\dy
- \Jsrc

Full solution example:

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\documentclass[a4paper,10pt]{article}

% enable advanced mathematics support
\usepackage{amsmath}

% enable pmatrix environment
\usepackage{mathtools}

% define custom mathematics commands
\newcommand{\dx}{\partial x}
\newcommand{\dy}{\partial y}
\newcommand{\Jsrc}{J_{src}}

% define \phantom shortcut
\newcommand{\p}[1]{\phantom{#1}}

\begin{document}

\[
  \begin{pmatrix*}[l]
    \p{-}(E_1 - E_2)/\dx \\
       - (E_3 - E_4)/\dy \\
       - \Jsrc
  \end{pmatrix*}
\]

\end{document}

[localghost]

I found an answer. […]

Then please mark the topic (not the last post) accordingly as written in Section 3 of the Board Rules (to be read before posting). A complete code example of your solution would be desirable to make it comprehensible for others.


Best regards and welcome to the board
Thorsten