I want to align the axes in (a) and (b) which I've marked on the picture, like they do in (c) and (d)?
The main code is below:
\begin{figure}[!t]
\centering
\subfloat[]{\includegraphics[width=1.5in]{pre_coherent_a.eps}%
\label{pre:a}}
\hfil
\subfloat[]{\includegraphics[width=1.5in]{pre_coherent_b.eps}%
\label{pre:b}}
\hfil
\subfloat[]{\includegraphics[width=1.5in]{pre_coherent_c.eps}%
\label{pre:c}}
\hfil
\subfloat[]{\includegraphics[width=1.5in]{pre_coherent_d.eps}%
\label{pre:d}}
\caption{Main processing stages of pre-coherent processing.}
\vspace{-10 pt} % adjust the vertical spacing
\label{fig_sim1}
\end{figure}