Latex equation problem by using MAC OS X Grapher

Question

I have used MAC OS X Grapher to create this equation:

\begin{equation}
\mbox{C}skip\left( \; d\;  \right)\; =\; \left\{\begin{array}{cc} 1+\mbox{C}m\cdot \left( Lm-d-1 \right), & if\; Rm\; =\; 1 \\ \frac{1+\mbox{C}m-Rm-\mbox{C}m\cdot Rm^{Lm-d-1}}{1-Rm}, & Otherwise \end{array}\right
\end{equation}

I should be something like this: enter image description here

But when I've tried to add the code in my latex file it doesn't work, I got some errors.

Can you help me please ?

Heiko Oberdiek · Answer 1 · 2015-07-03T09:05:03.270

4

\left and \right must be come in pairs, even if only one is needed. In this case the other delimiter is a period: \left\{ ... \right..

But code and result are so ugly, it is much easier to rewrite them from scratch. Package amsmath provides the environment cases, which is used here. The used symbols are based on some wild guesses (e.g., m as index, ...):

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
  C_{\textnormal{skip}}(d) =
  \begin{cases}
    1 + C_m (L_m - d - 1), & \text{if $R_m=1$} \\
    \frac{1 + C_m - R_m - C_m R_m^{L_m - d -1}}{1 - R_m},
    & \text{otherwise}
  \end{cases}
\end{equation}
\end{document}

The size of the fraction can be increased by \dfrac instead of \frac:

$Result \dfrac$

The environment dcases of package mathtools, see comment of Andrew Swann, also improves the vertical spacing:

edited Jul 03 '15 at 09:05

answered Jul 02 '15 at 22:17

Heiko Oberdiek

271,626

Yes you are right it was so ugly, because i just copied it from the Grapher tool directly. – user3653683 Jul 02 '15 at 22:48
Further simplification is to use dcases* from mathtools – Andrew Swann Jul 03 '15 at 07:23
@AndrewSwann Thanks, answer updated. It also improves the vertical spacing. – Heiko Oberdiek Jul 03 '15 at 07:44
Please do not promote the use of \text for C_{\text{skip}} as soon a this is used in an italic context this will be wrong. – daleif Jul 03 '15 at 08:21
1

@daleif I have changed it to \textnormal the only reasonable alternative, see question "Difference between various methods for producing text in math mode". Italic context with math is dead ugly. – Heiko Oberdiek Jul 03 '15 at 09:09
@HeikoOberdiek why not just \textup, shorter? – daleif Jul 03 '15 at 09:16
@daleif \textup is family sensitive. Then you would have typewriter in a \ttfamily context. – Heiko Oberdiek Jul 03 '15 at 09:37
@HeikoOberdiek but I think think you can make a case for both. If say a theorem design is in sans serif, it may look odd that a textual index comes up as non sans serif. – daleif Jul 03 '15 at 09:42
@daleif Then the same symbol changes its appearance, when used in a roman context again. IMHO the problem is such a design. Summary: a command that fits all needs does not exist. – Heiko Oberdiek Jul 03 '15 at 09:53
Very efficient , thank you all ... I will update it ... many thanks again – user3653683 Jul 03 '15 at 12:45

Latex equation problem by using MAC OS X Grapher

1 Answers1