Where is this whitespace coming from in align*?

Question

I am trying to align 2 simple equations using the align* environment:

\begin{align*}
\phi(\gedge{\tilde{v}_{i_1}}{\tilde{u}_i}) & = \phi(\gedge{\tilde{v}_{i_2}}{\tilde{u}_i}) & = \gedge{v}{u} \\
\phi(\gedge{\tilde{u}_i}{\tilde{v}_{i_1}}) & = \phi(\gedge{\tilde{u}_i}{\tilde{v}_{i_2}}) & = \gedge{u}{v} & \qquad\mathrm{(z\,wl.\,2)}\\
\end{align*}

unfortunately the result I am getting is horrible:

enter image description here

Why is there so much horizontal space before the second = sign?!?

Do not worry about \gedge, it is just an arrow:

% graph edge
\newcommand{\gedge}[2]{%
#1 \to #2%
}%

With align, you need only one &. If you want to use multiple alignment spots, you can use the alignat environment. — dustin, Jul 09 '13 at 21:46
related, if not exactly the same: Why does aligning equations not work here? — barbara beeton, Jul 09 '13 at 21:49

score 6 · Accepted Answer · edited Jun 12 '17 at 17:22

6

So you have two options,

Using align

\begin{align*}
\phi(\gedge{\tilde{v}_{i_1}}{\tilde{u}_i}) & = \phi(\gedge{\tilde{v}_{i_2}}{\tilde{u}_i}) = \gedge{v}{u} \\
\phi(\gedge{\tilde{u}_i}{\tilde{v}_{i_1}}) & = \phi(\gedge{\tilde{u}_i}{\tilde{v}_{i_2}}) = \gedge{u}{v}  \qquad\mathrm{(z\,wl.\,2)}\\
\end{align*}

Using alignat

\begin{alignat*}{4}
\phi(\gedge{\tilde{v}_{i_1}}{\tilde{u}_i}) & = \phi(\gedge{\tilde{v}_{i_2}}{\tilde{u}_i}) && = \gedge{v}{u} \\
\phi(\gedge{\tilde{u}_i}{\tilde{v}_{i_1}}) & = \phi(\gedge{\tilde{u}_i}{\tilde{v}_{i_2}}) && = \gedge{u}{v} & \qquad\mathrm{(z\,wl.\,2)}\\
\end{alignat*}

edited Jun 12 '17 at 17:22

David Carlisle

757,742

answered Jul 09 '13 at 21:48

dustin

18,617
23
99
204

The alignat solution should really use a double && to get the correct spacing. See for instance: Why does aligning equations not work here? – Peter Grill Jul 09 '13 at 22:05
@PeterGrill or couldnt {} be placed too? – dustin Jul 09 '13 at 22:13
For this specific case a {} would suffice, but not a general solution as it would still be r aligned, and an l aligned is probably what is desired in this case. See question I linked to. – Peter Grill Jul 09 '13 at 22:54
@PeterGrill Heiko Oberdiek added in && already. – dustin Jul 09 '13 at 23:10

Where is this whitespace coming from in align*?

1 Answers1