Math & Science ⇒ Horizontal Spacing in aligned Equations

[Pratt_G]

Hi,

can anyone please help me understand the following two issues?

1. Why do I get non-uniform and inordinate spacing between the columns? The first summation is very close to "min" and the second summation is way too from the first summation.
2. Is there any way to left-align the columns? I want the third columns to be aligned left.

Code: Select all

\documentclass[11 pt]{article}
\usepackage {amsmath}

\begin{document}
  \begin{subequations}
    \begin{align}
      \min\limits_{\lambda} & \sum\limits_{k \in R} & (\sum\limits_{i=1}^{M} a_i \quad +\\
      & & \sum \limits_{j=1}^N b_j \quad + \quad \sum       \limits_{j=1}^N c_j \quad +  \\
    \end{align}					 
  \end{subequations}
\end{document}

Thanks,
P

[localghost]

The alignat environment is your friend.

Code: Select all

\documentclass[11pt]{article}
\usepackage{mathtools}  % loads »amsmath«

\begin{document}
  \begin{subequations}
    \begin{alignat}{2}
      \min\limits_{\lambda} & \sum\limits_{k\in R} & \Big(\sum\limits_{i=1}^{M} a_i \quad + \\
     & \sum \limits_{j=1}^N b_j \quad + \quad &\sum\limits_{j=1}^N c_j \quad +
    \end{alignat}                                      
  \end{subequations}
\end{document}

Since there seem to be going more elements into the equations, you might need to choose another number as parameter for the environment.


Further reading:

• The »Math mode« document.

Best regards and welcome to the board
Thorsten

[Pratt_G]

Thanks. That worked. But in my general experience align and alignat have been very painful to use especially because their preset horizontal alignments. I prefer to use array instead, as it allows me to flexibly choose the alignment of individual columns. Now only if there was a way to use array under subequations environment.