Várias subfiguras alinhadas horizontalmente

Question

Estou tendo alguns problemas ao tentar exibir várias figuras alinhadas horizontalmente em uma mesma linha, estou usando os seguintes comandos do LaTeX e obtenho a seguinte figura fora do lugar:

\usepackage{caption}
\usepackage{subcaption}

\begin{figure}
    \centering
    \begin{subfigure}[a]{0.125\textwidth}
        \centering
        \includegraphics[width=\textwidth]{Boxplot_Profit_RandCA_Library_KPI_19_31181_Rules_8_Size_3.png}
        \caption{}
        \label{fig:}
    \end{subfigure}
    \hfill
    \begin{subfigure}[b]{0.125\textwidth}
        \centering
        \includegraphics[width=\textwidth]{Boxplot_Weight_RandCA_Library_KPI_19_31181_Rules_8_Size_3.png}
        \caption{}
        \label{fig:}
    \end{subfigure}
    \hfill
    \begin{subfigure}[c]{0.125\textwidth}
        \centering
        \includegraphics[width=\textwidth]{Boxplot_Profit_RandCA_Library_KPI_40_100000_Rules_8_Size_3.png}
        \caption{}
        \label{fig:f}
    \end{subfigure}
    \hfill
    \begin{subfigure}[d]{0.125\textwidth}
        \centering
        \includegraphics[width=\textwidth]{Boxplot_Weight_RandCA_Library_KPI_40_100000_Rules_8_Size_3.png}
        \caption{}
        \label{fig:}
    \end{subfigure}
    \hfill
    \begin{subfigure}[e]{0.125\textwidth}
        \centering
        \includegraphics[width=\textwidth]{Boxplot_Profit_RandCA_Library_KPI_60_100000_Rules_8_Size_3.png}
        \caption{}
        \label{fig:}
    \end{subfigure}
    \hfill
    \begin{subfigure}[f]{0.125\textwidth}
        \centering
        \includegraphics[width=\textwidth]{Boxplot_Weight_RandCA_Library_KPI_40_100000_Rules_8_Size_3.png}
        \caption{}
        \label{fig:}
    \end{subfigure}
       \caption{Six simple graphs}
       \label{fig:three graphs}
\end{figure}

Answer 1

Parece que você está procurando o seguinte:

Como mencionado @Miyase em seu comentário, você entendeu mal o significado das opções de subfiguras. Thea são importantes para sua colocação: t(para cima), c(para meio) e b(para baixo). Os rótulos de legenda são definidos por \captioncomando e o padrão são letras alfabéticas minúsculas a, b, c, etc. redefinidas em cada figure(ou table) float.

Portanto, o MWE da sua figura deve ser:

\documentclass{article}
\usepackage[font=small]{subcaption}
\usepackage{graphicx}

\begin{document}
    \begin{figure}[ht]
\setkeys{Gin}{width=\linewidth}
    \begin{subfigure}[t]{0.15\textwidth}
\includegraphics{example-image-duck}%{Boxplot_Profit_RandCA_Library_KPI_19_31181_Rules_8_Size_3.png}
\caption{}
\label{fig:}
    \end{subfigure}
\hfill
    \begin{subfigure}[t]{0.15\textwidth}
\includegraphics{example-image-duck}%{Boxplot_Weight_RandCA_Library_KPI_19_31181_Rules_8_Size_3.png}
\caption{}
\label{fig:}
    \end{subfigure}
\hfill
    \begin{subfigure}[t]{0.15\textwidth}
\includegraphics{example-image-duck}%{Boxplot_Profit_RandCA_Library_KPI_40_100000_Rules_8_Size_3.png}
\caption{}
\label{fig:f}
    \end{subfigure}
\hfill
    \begin{subfigure}[t]{0.15\textwidth}
\includegraphics{example-image-duck}%{Boxplot_Weight_RandCA_Library_KPI_40_100000_Rules_8_Size_3.png}
\caption{}
\label{fig:}
    \end{subfigure}
\hfill
    \begin{subfigure}[t]{0.15\textwidth}
\includegraphics{example-image-duck}%{Boxplot_Profit_RandCA_Library_KPI_60_100000_Rules_8_Size_3.png}
\caption{}
\label{fig:}
    \end{subfigure}
\hfill
    \begin{subfigure}[t]{0.15\textwidth}
\includegraphics{example-image-duck}%{Boxplot_Weight_RandCA_Library_KPI_40_100000_Rules_8_Size_3.png}
\caption{}
\label{fig:}
    \end{subfigure}
\caption{Six simple graphs}
\label{fig:three graphs}
    \end{figure}
\end{document}

Answer 2

Você pode definir o primeiro parâmetro subcaptionboxcomo vazio se não precisar de sublegenda, como \subcaptionbox{}{\includegraphics[width=.125\linewidth]{example-image}}.

\documentclass{article}
\usepackage{graphicx}
\usepackage{subcaption}
\begin{document}

\begin{figure}
\centering
\subcaptionbox{a1\label{a1}}{\includegraphics[width=.125\linewidth]{example-image}}\hfill
\subcaptionbox{a2\label{a2}}{\includegraphics[width=.125\linewidth]{example-image}}\hfill
\subcaptionbox{a3\label{a3}}{\includegraphics[width=.125\linewidth]{example-image}}\hfill
\subcaptionbox{a4\label{a4}}{\includegraphics[width=.125\linewidth]{example-image}}\hfill
\subcaptionbox{a5\label{a5}}{\includegraphics[width=.125\linewidth]{example-image}}\hfill
\subcaptionbox{a6\label{a6}}{\includegraphics[width=.125\linewidth]{example-image}}
\caption{bbb}
\label{bbb}
\end{figure}

\end{document}