4

I am using https://www.codecogs.com/latex/eqneditor.php

And added my latex as follows:

 \begin{equation}
 SSIM(x,y)=\frac{{\left ( 2 \mu_x\mu_y+ C_1 \right )+ \left (2 \sigma _x_y+C_2\right)}} 
{\left(\mu_x^2+\mu_y^2+C_1)(\sigma_x^2+\sigma_y^2+C_2\right)}
  \label{eq:SSMI}
\end{equation}

I expected the following formula but instead of I got the error:!Double subscript. ...y+C_1\right)+ ...

enter image description here

  • 4
    \sigma _x_y -> \sigma_{xy}. – CroCo Dec 9 '17 at 21:42
  • 2
    in addition to the subscript error, you should remove the \left and \right which are not wanted here – David Carlisle Dec 9 '17 at 21:45
6

Double subscripts are not allowed by TeX, you should replace \sigma_x_y by \sigma_{xy}.

Also, it is preferable to use a specific operator name for such a function.

Edit: And as David Carlisle pointed out, the \left and \right commands are of no use here. It can only add unwanted additional spacing.

You can try something like this:

\documentclass[12pt]{article}
%
\usepackage{mathtools}
\DeclareMathOperator{\SSIM}{SSIM}
\begin{document}
\begin{equation}
  \SSIM(x,y) = \frac{(2\mu_x\mu_y + C_1) + (2 \sigma _{xy} + C_2)} 
    {(\mu_x^2 + \mu_y^2+C_1) (\sigma_x^2 + \sigma_y^2+C_2)}
  \label{eq:SSMI}
\end{equation}
\end{document}

enter image description here

3

To achieve the desired output, simply replace \sigma _x_y by \sigma _{xy}.

  • Please make your answer self-contained, see minimal working example (MWE). – Henri Menke Dec 9 '17 at 21:40
  • I am thankfull to all. I try to rewrite with \DeclareMathOperator it didnt work :( What is the purpose of using it? For example after declared the formula may I call it just writing SSMI etc? – user8151324 Dec 9 '17 at 22:01
  • Errors: Can be used only in preamble.... undefined control sequence declaremath and SSIM – user8151324 Dec 9 '17 at 22:09
  • @user8151324 You have to load the amsmath package or its extension mathtools, as I did, to use the DeclareMathOperator command. It is a typographical convention that math operators should be typesetted in roman type, like the main text, hence this command. See the amsmath documentation for more information. – Franck Pastor Dec 9 '17 at 22:12
  • I have all: \usepackage{float} \usepackage{amsmath} \usepackage{mathtools} \usepackage{caption} \usepackage{subcaption} \usepackage{placeins} \usepackage{epstopdf} \usepackage{multirow} – user8151324 Dec 9 '17 at 22:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.