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I want to code this equation in LaTeX:


I'd like to know how to code the equation and the description below it with a reference as well.

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It would be useful to know what you have up to now. – egreg Apr 26 '12 at 18:00
I'm pretty new to latex. My main query is how to put the dash above an alphabet, the big dash for division and the description as written here. – Rohan Apr 26 '12 at 18:06
up vote 12 down vote accepted

Even though your question was thoroughly answered here's my solution, it differs only in not using a table but a list:





\[ P_{xi}=\overline{U_{x}}+\sigma_{x}\frac{\sum^{Nu}_{k}D_{kx}\times 
    \left( \frac{S_{ki}-\overline{U_{k}}}{\sigma_{k}}\right)}{\sum^{Nu}_{k}D_{kx}} \]
    \item $P_{xi}$: is the predicted rate for user $x$ on item $i$
    \item $S_{ki}$: is the rate of song $i$ given by user $k$
    \item $\overline{U_{x}}$: is the average rate of user $x$
    \item $\overline{U_{k}}$: is the average rate of user $k$
    \item $\sigma_{x}$: is the standard deviation of all the rates of user $x$


Which produces the following result: Equation and description

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You can use \item[$P_{xi}$] to set the label as the symbol - this makes sure the items align – Henrik Hansen Apr 27 '12 at 7:59

Some more flair in managing the "where" clause, and formatting of the conditions:

enter image description here

\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\usepackage{array}% http://ctan.org/pkg/array

  \begin{tabular}{>{$}r<{$}@{\ :\ }l}
    P_{xi} & is the predicted rate for user~$x$ on item~$i$ \\
    S_{ki} & is the rate of song~$i$ given by user~$k$ \\
    D_{kx} & the correlation between user~$x$ and user~$k$ \\
    \overline{U}_x & the average rate over user~$x$ \\
    \overline{U}_k & the average rate over user~$k$ \\
    \sigma_x & is the standard deviation of all the rates of user~$x$

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Another option is to use \shortinertext from the mathtools package as that provides tighter vertical spacing. – Peter Grill Apr 26 '12 at 18:40
I did not know you could set which columns were math mode in tabular. That's really cool. – EricR May 1 '12 at 20:21
@EricR: All thanks to the array package using the > and < "directive". :) – Werner May 1 '12 at 20:23

You can add the line over the variables using \overline. The text below can be done e.g. using a tabular.


    P_{xi} = \overline{U_{x}} + \sigma_{x} \frac
    {\sum_k^{Nu} D_{kx} \times \left( \frac {(S_{ki}-\overline{U_k})}{\sigma_k} \right) }
    {\sum_k^{Nu} D_{kx}},
    $P_{xi}$:& is the predicted rate for user $x$ on item $i$. \\
    $S_{ki}$:& is the rate of song $i$ given by user $k$. \\
    ... & ... \\



You can change the space between the columns in the tabular by adding @{\hspace{<your space>}} between the r and l column type specifier.

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I wouldn't overline also the subscript. – egreg Apr 26 '12 at 19:27
@egreg: Yes, I agree. I had it different at first myself. I tend to replicate requested things as closely as possible. Bad engineering habit ... – Martin Scharrer Apr 26 '12 at 19:45

If you want to create a numbered equation as in your example, put the math part in an equation environment and add a \label that can be used to reference the equation later (with \ref{}). The LaTeX code of your equation could look like this:


enter image description here

Of course, you can tweak it to your liking, e.g. put the sum limits above/below the sum (append \limits to the \sum command) or use bigger sum symbols. You should have a look into one of the many LaTeX books available to familiarize yourself with the system.

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