64

In an equation, I want to display three points like "...", but instead of horizontally, they should be diagonally. I'm sure there must be a command to do that, but a google search did not really help.

Any idea?

6
  • 7
    "\ddots"; see also detexify.kirelabs.org/classify.html
    – Grigory M
    Aug 9, 2010 at 8:31
  • That's what I was looking for Grigory M. Thank you. Put it in an answer so I can accept it...
    – Nigu
    Aug 9, 2010 at 8:41
  • I looked in the tables.pdf file provided with texshop, but didn't find this specific command. I'll have a look at your other references...
    – Nigu
    Aug 9, 2010 at 8:42
  • @Grigory: We have had lots of questions for symbols which were easily resolved by detexify or symbols. I think it is better to answer them and add a link to detexify, symbols or the general questions, than to close them. However, you can open a question on meta to discuss this.
    – Caramdir
    Aug 9, 2010 at 8:44
  • well, it's proposed as FAQ entry on meta — but while it's not in FAQ, I guess you're right: we'll have to answer such questions
    – Grigory M
    Aug 9, 2010 at 8:46

4 Answers 4

65

The command is called \ddots. See also How to look up a symbol or identify a math symbol or character? (esp. detexify).

4
  • Perhaps it's a good place to state that Detexify apparently runs a cryptocurrency miner
    – hola
    Aug 5, 2020 at 7:32
  • @xxx--- [citation needed]
    – Grigory M
    Aug 5, 2020 at 9:27
  • There you go: tug.org/mail-archives/texhax/2011-June/017593.html
    – hola
    Aug 5, 2020 at 12:15
  • Maybe it was true 10 years ago — but nowadays detexify doesn't load anything from bitp.it (AFAICS). Also it uses very little of [client's] computer's resources — so I'm skeptical.
    – Grigory M
    Aug 5, 2020 at 13:41
32

According to http://www.tex.ac.uk/cgi-bin/texfaq2html?label=mathlips

The mathdots package (besides fixing up the behaviour of (La)TeX \ddots and \vdots when the font size changes) provides an “inverse diagonal” ellipsis \iddots

That is, \iddots is three dots sloping forwards while \ddots is three dots sloping backwards.

1
  • 3
    Codecogs doesn't support \iddots May 15, 2016 at 23:38
8

An alternative to the \iddots (inverse diagonal dots) from the mathdots package:

\makeatletter
\def\Ddots{\mathinner{\mkern1mu\raise\p@
\vbox{\kern7\p@\hbox{.}}\mkern2mu
\raise4\p@\hbox{.}\mkern2mu\raise7\p@\hbox{.}\mkern1mu}}
\makeatother

Then call with \Ddots

0
0

It's not perfect but you can use \dots and \cdot and align them using subscript _ and superscript ^ as demonstrated in row 2 below.

You get the vertical dots on row 1 as a bonus since the need to write diagonal dots are typically related to building a "dotted" matrix like in the picture below.

\newcommand{\vertdots}{\underset{\big{\overset{\cdot}{\cdot}}}{\cdot}} 
\newcommand{\diagdots}{_{^{\big\cdot}\cdot _{\big\cdot}}}

\begin{equation*}
A = \begin{bmatrix} 
a           & \dots         & b         \\ 
\vertdots   &  \diagdots    & \vertdots \\
c           & \dots         & d         \\
\end{bmatrix}
\end{equation*}

This produces a matrix that looks like this:

enter image description here

I tried to align the diagonal dots better but didn't succeed. This will be good enough for me.

2
  • Why not using \cdots for the horizontal dots?
    – Elmex80s
    Dec 18, 2020 at 15:59
  • I can't remember right now, but I think they didn't line up properly. But maybe it'll work. Dec 18, 2020 at 21:12

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