equations
I want to write tensorial equations in latex indicating the equivalent indices as shown below:
Here I have used MS Powerpoint to make these images. Although it works, using this means I cannot use equation numbering in latex and relevant tags. And editing these becomes a pain.
Things I need –
\underbracket type functionality joining the individual index lines and should allow for overlappingIs there a more elegant solution, preferably using only latex?
Put everything in one align environment, don't enclose this in an equation environment, and use \nonumber on lines that should not be numbered.
\documentclass{article}
\usepackage{mathtools}
\begin{document}
\begin{align}
\frac{\partial s}{\partial W}
&= \frac{\partial \sum_{i=1}^{n} (y_i -(W\cdot x_i+b))^2}
{\partial W} \nonumber \\
&= \sum_{i=1}^{n} 2(y_i -W\cdot x_i-b)\cdot(-x_i))
= 2\cdot \sum_{i=1}^{n} (-y_i\cdot x_i + W\cdot x_i^2 + b\cdot x_i )
\stackrel{!}{=} 0 \nonumber\\ \nonumber\\
&\Longleftrightarrow W\cdot(\sum_{i=1}^{n} x_i^2) + b\cdot(\sum_{i=1}^{n}x_i)
= \sum_{i=1}^{n}x_i\cdot y_i \label{eq:4: Partial W } \\
\frac{\partial s}{\partial b}
&= \frac{\partial \sum_{i=1}^{n} (y_i -(W\cdot x_i+b))^2}
{\partial b} \nonumber \\
&= \sum_{i=1}^{n} 2(y_i -W\cdot x_i-b)\cdot(-1))
= 2\cdot \sum_{i=1}^{n} (-y_i\cdot+ W\cdot x_i+ b)
\stackrel{!}{=} 0 \nonumber \\ \nonumber \\
&\Longleftrightarrow W\cdot(\sum_{i=1}^{n} x_i) +\sum_{i=1}^{n}b
= \sum_{i=1}^{n} y_i \nonumber \\
&\Longleftrightarrow W\cdot(\sum_{i=1}^{n}x_i) + n\cdot b
= \sum_{i=1}^{n} y_i \label{eq:5: Partial b }
\end{align}
\end{document}
You have two options; either use (\ref{..}) or \eqref{..} as noted out by @marmot in a comment. The latter requires adding amsmath in your preamble.
\documentclass[a4paper,12pt]{article}
\usepackage{amsmath} % <-- for \eqref
\begin{document}
\begin{equation}\label{Emc2}
E=mc^2
\end{equation}
Einstein wrote his famous equation (\ref{Emc2}), blah blah blah ....
Einstein wrote his famous equation \eqref{Emc2}, blah blah blah ....
\end{document}
Best Answer
Welcome to TeX.SE!! I think this is a possible solution, but I'm not very sure about you point 2. I don't know how the lines must 'indicate the number of indices'.
However I hope this helps. I made two
pics. I call the firstvlineswhich draw those vertical lines that must 'indicate the number of indices'. Thispictakes a parameter: the number of lines to draw. If it's not present draws exactly 2 lines. The secondpic,underbracketdraw a line connecting two nodes (created in the equations with\tikzmarknode). Thispicneeds four parameters: end point, x shift in the initial point, x shift in the final point and y shift.Something like this:
Edit: I changed the second
picfor astyleinspired in Andrew Stacey's answer in this post. It does the same but I think that the syntax is a little bit clearer.And the new code: