Subcaptions not aligned under each subfigure

Question

I currently have a figure that contains two subfigures. I want to add labels underneath each subfigure but I'm having trouble aligning them. The first subcaption seems to center from the perspective of both subfigures (i.e., the entire page) which leads to the second subcaption starting from what I assume is a new line. More specifically, the code that I have is:

\documentclass[10pt,journal,compsoc]{IEEEtran}

% *** SUBFIGURE PACKAGES ***
\ifCLASSOPTIONcompsoc
 \usepackage[caption=false,font=footnotesize,labelfont=sf,textfont=sf]{subfig}
\else
 \usepackage[caption=false,font=footnotesize]{subfig}
\fi
% subfig.sty, written by Steven Douglas Cochran, is the modern replacement
% for subfigure.sty, the latter of which is no longer maintained and is
% incompatible with some LaTeX packages including fixltx2e. However,
% subfig.sty requires and automatically loads Axel Sommerfeldt's caption.sty
% which will override IEEEtran.cls' handling of captions and this will result
% in non-IEEE style figure/table captions. To prevent this problem, be sure
% and invoke subfig.sty's "caption=false" package option (available since
% subfig.sty version 1.3, 2005/06/28) as this is will preserve IEEEtran.cls
% handling of captions.
% Note that the Computer Society format requires a sans serif font rather
% than the serif font used in traditional IEEE formatting and thus the need
% to invoke different subfig.sty package options depending on whether
% compsoc mode has been enabled.
%
% The latest version and documentation of subfig.sty can be obtained at:
% http://www.ctan.org/pkg/subfig

\usepackage{caption}
\usepackage{subcaption}


\begin{figure*}[!t]
    \begin{subfigure}
        \centering
        \includegraphics[trim={0, 0, 0, 0}, width=\columnwidth]{figures/plot1.pdf}
        \subcaption{Thing}
    \end{subfigure}
    \begin{subfigure}
        \centering
        \includegraphics[trim={0, 0, 0, 0}, width=\columnwidth]{figures/plot2.pdf}
        \subcaption{Thing}
    \end{subfigure}
\caption{Something.}
\label{fig:attention_score}
\end{figure*}

which leads to this:

I've read from this answer that the subfigure takes an option for a subcaption anchor, and I accordingly added a [c] to the right of each \begin{subfigure}. That leads to this:

Neither image is what I want. How should I configure things so that each subcaption is centered directly beneath each subfigure? Thanks.

Answer 1

Your MWE loads the subfig as well as the subcaption package resulting in error messages such as:

! Package subcaption Error: This package can't be used in cooperation with the subfig package.

To overcome this, remove the subcaption package and use \subfloat instead of the subfigure environment, as shown in the following example:

\documentclass[10pt,journal,compsoc]{IEEEtran}

% *** SUBFIGURE PACKAGES ***
\ifCLASSOPTIONcompsoc
 \usepackage[caption=false,font=footnotesize,labelfont=sf,textfont=sf]{subfig}
\else
 \usepackage[caption=false,font=footnotesize]{subfig}
\fi

\usepackage[demo]{graphicx}% remove the demo option in your actual document.

\begin{document}


\begin{figure*}[!t]
\subfloat[Thing.]{\includegraphics[width=\columnwidth]{figures/plot1.pdf}}
\hfill
\subfloat[Thing.]{\includegraphics[width=\columnwidth]{figures/plot2.pdf}}
\caption{Something.}
\label{fig:attention_score}
\end{figure*}

\end{document}

Answer 2

Your test document must be generating several error messages of the following type -- don't ignore them!

./main.tex:10: Missing number, treated as zero.
<to be read again> 
\protect 
l.10         \centering
                     
? 

These messages are generated because of a syntax error in your code: you failed to provide the mandatory width argument of the subfigure environments.

How to fix this? Instead of just \begin{subfigure}, you should write \begin{subfigure}{\columnwidth}.

Once these syntax errors are fixed, the test document compiles without further ado. Just for extra code hygiene, though, I'd remove (or comment out) the two redundant \centering instructions and insert an \hfill directive between the two subfigure environments in order to maximize their horizontal separation.

\documentclass[twocolumn]{article}
\usepackage{subcaption}
\usepackage[demo]{graphicx} % remove 'demo' option in real document

\begin{document}

\begin{figure*}
    \begin{subfigure}{\columnwidth} % <-- added '{\columnwidth}'
        %\centering % redundant
        \includegraphics[trim={0, 0, 0, 0}, width=\columnwidth]{figures/plot1.pdf}
        \subcaption{Thing 1}
    \end{subfigure}%
    \hfill % <-- maximize horizontal separation (subject to text block width constraint)
    \begin{subfigure}{\columnwidth} % <-- added '{\columnwidth}'
        %\centering % redundant
        \includegraphics[trim={0, 0, 0, 0}, width=\columnwidth]{figures/plot2.pdf}
        \subcaption{Thing 2}
    \end{subfigure}
\caption{Something.}
\label{fig:attention_score}
\end{figure*}

\end{document}

Answer 3

\documentclass[12pt]{report}
\usepackage[letterpaper,top=1in,bottom=1in,right=1in,left=1in]{geometry}
    \usepackage[demo]{graphicx}
\usepackage{subcaption}
    \begin{document}
        \begin{figure}[h]
                    \begin{subfigure}[t]{0.45\textwidth}
                    \includegraphics[trim={0, 0, 0, 0}, width=\textwidth]{gfx-1}
                    \caption{Caption 1}
                \end{subfigure}
                \hfill
                    \begin{subfigure}[t]{0.45\textwidth}
                        \includegraphics[trim={0, 0, 0, 0}, width=\textwidth]{gfx-1}
                        \caption{Caption 2}
                    \end{subfigure}
        \caption{center caption}
        \end{figure}
    \end{document}