citep not working with apacite

Question

I am unable to make use of the \citep{} function on LaTeX, using Texmaker. \cite{} works just fine, however.

\documentclass[11pt]{article}
\usepackage{graphicx}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{authblk}
\usepackage{amssymb}
\usepackage{apacite}
\usepackage{float}
\usepackage{amsmath}
\usepackage{setspace}
\usepackage{fullpage}
\usepackage{graphicx, subfigure}
\usepackage{setspace}
\graphicspath{ {./Images/} }
\usepackage{url}
\usepackage{rotating}
\usepackage{adjustbox}
\usepackage{lmodern,microtype}
%\usepackage{titlesec,titling}
\usepackage{enumitem,booktabs}
\usepackage{pstricks}
\usepackage{amsmath,amsthm,amssymb,amsfonts}
\usepackage{dsfont,mathrsfs,ushort}
\usepackage[utf8]{inputenc}
\usepackage{tabularx} 
\usepackage[toc,page]{appendix}
\usepackage{xcolor}
\usepackage{sectsty}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric,arrows}


\tikzstyle{process}=[rectangle,minimum width=3cm,minimum height=1cm, text centered, draw=black, fill=orange!30]
\tikzstyle{decision}=[diamond,minimum width=3cm, minimum height=1cm, text centered, draw=black, fill=green!30]

\tikzstyle{arrow}=[thick,->,>=stealth]
\newcommand*{\myplus}{\ensuremath{\boldsymbol{\pmb{+}}}}


\chapterfont{\color{blue}}  % sets 
\sectionfont{\color{blue}}  % sets colour of sections
\subsectionfont{\color{red}}  % sets colour of sections


\begin{document}

\chapter{citations}

\begin{enumerate}
  \Citation 1 \cite{a1}.
  \Citation2 \citep{a2}.
\end{enumerate}

\bibliographystyle{apacite}
\bibliography{References}


\end{document}

Any help on this is much appreciated!

Answer 1

The apacite package knows three modes of operation with respect to citation commands.

1. Its default behaviour is that of the option apaciteclassic, which defines a set of citation commands useful for APA style. The main commands are \cite, \citeA and \citeNP.
2. The package option natbibapa loads natbib and thus enables use of natbib's citation commands \citet, \citep etc.
3. The option nocitation defines no new citation commands and is intended to be used by users who want to define their own commands or who want to try to use the apacite package with a third-party citation package.

See p. 7 of the apacite documentation.

In your MWE you load apacite without options as \usepackage{apacite} and hence you get the default behaviour of apaciteclassic. That means that natbib's \citet and \citep are not available, but you can use \cite, \citeA and \citeNP.

\documentclass[11pt]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{apacite}

\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@book{appleby,
  author  = {Humphrey Appleby},
  title   = {On the Importance of the Civil Service},
  year    = {1980},
}
\end{filecontents}

\begin{document}
\cite{appleby}

\citeA{appleby}

\citeNP{appleby}

\bibliographystyle{apacite}
\bibliography{\jobname}
\end{document}

If you want to be able to use \citep and \citet, you need to load the package with the natbibapa option.

\documentclass[11pt]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[natbibapa]{apacite}

\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@book{appleby,
  author  = {Humphrey Appleby},
  title   = {On the Importance of the Civil Service},
  year    = {1980},
}
\end{filecontents}

\begin{document}
\citet{appleby}

\citep{appleby}

\bibliographystyle{apacite}
\bibliography{\jobname}
\end{document}

---

If you are willing to switch to biblatex, you can use biblatex-apa and make use of biblatex's set of citation commands as suggested by Bernard in the comments.

\documentclass[11pt]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[style=apa, backend=biber]{biblatex}

\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@book{appleby,
  author  = {Humphrey Appleby},
  title   = {On the Importance of the Civil Service},
  year    = {1980},
}
\end{filecontents}
\addbibresource{\jobname.bib}

\begin{document}
\cite{appleby}

\parencite{appleby}

\textcite{appleby}

\printbibliography
\end{document}

Note that this requires Biber instead of BibTeX, see Biblatex with Biber: Configuring my editor to avoid undefined citations.