LaTeX forum ⇒ Math & Science ⇒ How to align Items in a Sum?

[Cham]

I'm having a small alignment problem with the idex of a sum :

Code: [Select all] [Expand/Collapse] [Download] (untitled.tex)

\sum_{\substack{i,\, j \,=\, 1 \\ j \, \ne \, i}}  A_{ij}

The = and \ne signs aren't properly aligned. How should we modifity that code to align the items properly ?

[localghost]

You can insert a vertical phantom, that is to say an appropriate box with hidden content.

Code: [Select all] [Expand/Collapse] [Download] (untitled.tex)

\documentclass[11pt,a4paper]{article}
\usepackage{amsmath}
 
\begin{document}
   \[
     \sum_{\substack{i,\, j\,=\, 1 \\ \hphantom{i,} j\,\ne\, i}}  A_{ij}
   \]
\end{document}

Thorsten

[Cham]

You can insert a vertical phantom

I tried it. The alignment isn't perfect.

[localghost]

Works fine for me. Please clarify in which way this is not satisfactory.

[Cham]

Works fine for me. Please clarify in which way this is not satisfactory.

The "=" and "\ne" aren't exactly aligned. If you compile and watch the index closely, you'll notice a small (and noticeable) offset. It's ugly.

[localghost]

I can't comprehend this.

[Stefan Kottwitz]

Hi Cham,

since equations/inequalities have to be aligned at a relation symbol, you could use an aligned environment. Also here you can customize size and fine-tune spacing. For example:

Code: [Select all] [Expand/Collapse] [Download] (untitled.tex)

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
   \sum_{\scriptsize\begin{aligned}i, j &= 1 \\[-4pt] j &\ne i\end{aligned}}  A_{ij}
\]
\end{document}

Btw. Thorstens way with a phantom command is handy in many situations.

Stefan

[Cham]

Hi Cham,

since equations/inequalities have to be aligned at a relation symbol, you could use an aligned environment. Also here you can customize size and fine-tune spacing. For example:

Code: [Select all] [Expand/Collapse] [Download] (untitled.tex)

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
   \sum_{\scriptsize\begin{aligned}i, j &= 1 \\[-4pt] j &\ne i\end{aligned}}  A_{ij}
\]
\end{document}

This code works fine. Thanks a lot for it !

[Cham]

I'm getting some warning messages in the log file about the previous formula :

LaTeX Font Warning: Command \scriptsize invalid in math mode on input line 222.

The formula associated to this warning message is this :

Code: [Select all] [Expand/Collapse] [Download] (untitled.tex)

\sum_{\scriptsize\begin{aligned} i, j &= 1 \\[-4pt] i &\ne j \end{aligned}}

Apparently, the \scriptsize command is not allowed, while the compiled formula is nicely looking on the PDF version. What's going on here ?

Is there a better way to code that double-sum, without getting that warning message ?