Formatting in Latex - Pseudocode

Question

I am trying to create a kind of pseudocode in Latex resembling the one shown below .

What I tried is:

1. Convert R to a binary region using the threshold $\theta_{0}$\\

2. Assume N is the sum of the number of non-zero pixels within $F_{l}$ and $F_{r}$.\\

3. If N is larger than a predefined threshold $\beta$, then\\

            \begin{center}
            $\theta_{0} = \theta_{0} + \Delta\theta$\\
            Repeat the procedure from step 1
            \end{center}
   Else

            \begin{center}
            $\theta = \theta_{0}$
            \end{center}
   End

Its not turning out like I want though. Can anyone please suggest how to fix this?

Answer 1

Here is an algorithm2e implementation:

\documentclass{article}
\usepackage{algorithm2e}
\LinesNumbered% Number algorithm lines
\usepackage{amsmath}
\begin{document}

\begin{algorithm}[H]
  \SetAlgoLined
  \KwData{$R$, $\beta$}
  \KwResult{$\theta_0$}
  Convert~$R$ to a binary region using the threshold $\theta_{0}$\; \label{first_step}
  Assume~$N$ is the sum of the number of non-zero pixels within~$F_l$ and~$F_r$\;
  \eIf{\text{$N$ is larger than a predefined threshold~$\beta$}}{
    $\theta_{0} = \theta_{0} + \Delta\theta$\;
    Repeat the procedure from Step~\ref{first_step}\;
  }{
    $\theta = \theta_{0}$\;
  }  
  \caption{How to write algorithms}
\end{algorithm}

\end{document}

Answer 2

A “hand made” solution reproducing the layout you showed

\documentclass{article}
\usepackage{enumitem}
\newlist{pseudocode}{enumerate}{2}
\setlist[pseudocode,1]{label=\arabic*.,ref=\arabic*}
\setlist[pseudocode,2]{label={},ref=\arabic*,nosep}

\begin{document}

\begin{pseudocode}
\item\label{step:convert} Convert $R$ to a binary region using the threshold $\theta_{0}$.

\item Assume $N$ is the sum of the number of non-zero pixels within $F_{l}$ and $F_{r}$.

\item If $N$ is larger than a predefined threshold $\beta$, then
    \begin{pseudocode}
    \item $\theta_{0} = \theta_{0} + \Delta\theta$
    \item Repeat the procedure from step \ref{step:convert}
    \end{pseudocode}
  Else
    \begin{pseudocode}
    \item $\theta = \theta_{0}$
    \end{pseudocode}
  End
\end{pseudocode}
where $\Delta\theta$, $\beta$ are two constants.

\end{document}

Answer 3

The easiest way is to use {enumerate} and the normal equation environments ({equation} and {gather} in this case – the * prevents numbering). The fleqn document class option sets the equations left aligned; omit this options to center them.

\documentclass[fleqn]{article}

\usepackage{mathtools}

\begin{document}
\begin{enumerate}
\item Convert R to a binary region using the threshold $\theta_{0}$
\item Assume N is the sum of the number of non-zero pixels within $F_{l}$ and $F_{r}$.
\item If N is larger than a predefined threshold $\beta$, then
    \begin{gather*}
    \theta_{0} = \theta_{0} + \Delta\theta\\
    \text{Repeat the procedure from step 1}
    \end{gather*}
    Else
    \begin{equation*}
    \theta = \theta_{0}
    \end{equation*}
    End
\end{enumerate}
\end{document}

More information can be found in the package manuals and LaTeX beginners books ;-)

Answer 4

BINGO!!! I created a solution! Works like a charm :) Remember to use: \usepackage{algpseudocode}

\begin{algorithmic}
\State Convert R to a binary region using the threshold $\theta_{0}$\\

\State Assume N is the sum of the number of non-zero pixels within $F_{l}$ and $F_{r}$\\

\If {$N \textgreater \beta$}
    \State $\theta_{0} = \theta_{0} + \Delta\theta$
    \State Repeat the procedure from step 1
\Else
    \State $\theta = \theta_{0}$
\EndIf

\end {algorithmic}