我正在尝试在文档中添加方程式的定义。我知道以前有人问过这个问题，我找到了一个很棒的解决方案。但对我来说，它不起作用。
这就是我发现的
\documentclass{article}
\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\usepackage{array}% http://ctan.org/pkg/array
\begin{document}
\begin{gather}
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}},
\intertext{Where:}
\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~$x$
\end{tabular}\nonumber
\end{gather}
\end{document}
我尝试这样做：
\begin{gather}
dN/d(d_{p}) = kd_{p}^{\delta},
\intertext{Where:}
\begin{tabular}{>{$}r<{$}@{\ :\ }l}
dN : number of particles per unit water volume in the size range d p to [d p +d(d p )] \
k : (= constant) depending on the particle concentration \
\delta : (< 0) descriptor of the distributions' spectral slope.
\end{tabular}\nonumber
\end{gather}
如果我输入“&”，latex 会告诉我，列数不够。此外，“\”不会显示为红色。我认为问题出在 {>{$}r<{$}@{\ :\ }l} 部分。但我不明白这里面发生了什么。
非常感谢您的帮助。
谢谢
答案1
\\你已经被这个网站臭名昭著的漏洞咬了，看看双反斜杠从代码中消失
您从以下位置复制了代码
https://tex.stackexchange.com/a/53483/4427
受该错误影响。以下是修复后的代码。
\documentclass{article}
\usepackage{amsmath}
\usepackage{array}
\begin{document}
\begin{gather}
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}},
\intertext{Where:}
\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~$x$
\end{tabular}\nonumber
\end{gather}
\end{document}
您尝试的固定代码应该是
\begin{gather}
dN/d(d_{p}) = kd_{p}^{\delta},
\intertext{Where:}
\begin{tabular}{>{$}r<{$}@{\ :\ }l}
dN & number of particles per unit water volume in the \\
\multicolumn{1}{c}{} & size range $dp$ to $[dp+d(dp)]$ \\
k & (constant) depending on the particle concentration \\
\delta & ($<0$) descriptor of the distributions' spectral slope.
\end{tabular}\nonumber
\end{gather}
答案2
这里有一种方法可能有用：
使用[t]on 选项tabular可获得更好的间距，tabular如 campa 的评论所述。但是，根据 egreg 的说法，这可能会影响段落间距，但我无法看到此问题，因此发布了：无法复制问题：使用[t]表格选项会影响段落间距。
代码：
\documentclass{article}
\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\usepackage{array}% http://ctan.org/pkg/array
\begin{document}
\[
dN/d(d_{p}) = kd_{p}^{\delta},
\]
where:
\begin{tabular}[t]{r@{}l}
$dN$ &: number of particles per unit water volume in the size range $d p$ to $[d p +d(d p )]$ \\
$k$ &: (= constant) depending on the particle concentration \\
$\delta$ &: $(< 0)$ descriptor of the distributions' spectral slope.
\end{tabular}
\end{document}
答案3
另一种解决方案，基于framed和description环境（语义上更令人满意）。另外，我认为d微分的和的d符号d_p有点令人困惑，所以我决定将微分“d”竖起来，使用在这个网站上找到的宏
\documentclass{article}
\renewcommand*{\d}{\mathop{\kern0pt\mathrm{d}}\!{}}
\usepackage{enumitem, framed}
\newenvironment{myleftbar}{%
\def\FrameCommand{{\hspace{0.8cm}\vrule width 0.5pt}\hspace{6pt}}%\
\MakeFramed {\advance\hsize-2\width \FrameRestore}\noindent\hspace{- 0.4em}}%
{\endMakeFramed}
\newenvironment{eqdescription}{%
\myleftbar
\llap{\makebox[1.4cm][l]{where: }}\vspace*{-\dimexpr\baselineskip + \topsep}\strut
\description[font=\normalfont, labelwidth=0.5cm, align=right, leftmargin=!, itemsep=0pt]
}
{%
\enddescription\vspace*{-\topsep}
\endmyleftbar}
\begin{document}
\[
\d N/\d(d_{p}) = kd_{p}^{\delta},
\]
\begin{eqdescription}
\item[$\d N$:] number of particles per unit water volume\\ in the size range $d_p$ to $[d_p +\d(d_p )]$,
\item[$k$:] (= constant) depending on the particle concentration,
\item[$\delta$:]$(< 0)$ descriptor of the distributions' spectral slope.
\end{eqdescription}
\end{document}
