# summation line for multiple rows

Is there a way to add multiple lines of numbers using a "summation line"? Specifically, I want to create something like the below, only better looking.

\documentclass{article}
\usepackage{fontspec,booktabs}
\setmainfont{TeX Gyre Termes}

\begin{document}
\begin{tabular}{ @{} c @{ } c @{ } c @{ } c @{ } c @{ } c @{ } c @{} }
$f(x=1)$ & $=$ & $\sum_{y}f(x=1, y)$ & $=$ & $0,2 + 0,1$ & $=$ & 0,3\\
$f(x=2)$ & $=$ & $\sum_{y}f(x=2, y)$ & $=$ & $0,3 + 0,1$ & $=$ & 0,4\\
$f(x=3)$ & $=$ & $\sum_{y}f(x=3, y)$ & $=$ & $0,1 + 0,2$ & $=$ & 0,3\\
&     &                     &     &             & $+$ &    \\\cmidrule(l){6-7}
&     &                     &     &             &     & 1,0\\
\end{tabular}
\end{document}


I am not interested in doing row or column based mathematical operations. I just want to create a nicer looking summation rule (instead of the one on the lower right part of the table).

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I think tex.stackexchange.com/q/3851/15925 should answer your question. –  Andrew Swann Apr 17 '13 at 12:09
Well, no, because my question is about creating a nice looking summation rule (the one on the lower right part) rather than actually doing mathematical operations. –  laissezfaire Apr 17 '13 at 12:27
Thanks for the clarification. –  Andrew Swann Apr 17 '13 at 12:31

I am used to the plus being to the right of the last line being summed. This can be acheived with:

\documentclass{article}
\usepackage{booktabs}

\begin{document}

\begin{tabular}{@{}c@{ }c@{ }c@{ }c@{ }c@{ }c@{ }c@{\hspace{0.5em}} c}
$f(1)$ & $=$ & $\sum_{y}f(1, y)$ & $=$ & $0{,}2 + 0{,}1$ & $=$ & 0{,}3 &         \\
$f(2)$ & $=$ & $\sum_{y}f(2, y)$ & $=$ & $0{,}3 + 0{,}1$ & $=$ & 0{,}4 &         \\
$f(3)$ & $=$ & $\sum_{y}f(3, y)$ & $=$ & $0{,}1 + 0{,}2$ & $=$ & 0{,}3 & $$+$$ \\ \cmidrule(r){7-8}
&     &                   &     &             &     & 1{,}0 &         \\
\end{tabular}

\end{document}


adding an extra column to hold the plus sign. I have also written {,} for better spacing on your decimal separator, and removed the x=.

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Looks neat ...although this trades an extra row for an extra column. I guess there is no better way to draw this sort of thing (i.e. using math commands) –  laissezfaire Apr 18 '13 at 5:06
By the way, how do you make your LaTeX output appear on the webpage? –  laissezfaire Apr 18 '13 at 5:07
For posting output, I convert to an image and upload, see meta.tex.stackexchange.com/q/2781/15925 . As for the layout, if you can make an image/draw what you want, that would be helpful. It is not clear to me whereelse is sensible placing for the + sign. Alternatively you put something like the word "Total" or "Sum" (in the column) before the final result. –  Andrew Swann Apr 18 '13 at 7:07