Ndtyhij

I am trying to get two rows with two figures in each row using subfigure, but I keep getting errors for this.

documentclass[demo]{article} % remove 'demo' option in real document

usepackage{graphicx,subcaption}

begin{document}

begin{figure}



begin{subfigure}[0.45textwidth]

    includegraphics[width=textwidth]{long_pneumonic.jpg}

    caption{Pre-vaccination susceptible and infected 

    population$alpha=0.000015, beta=0.0027, delta=.002, sigma=1/3, 

    Delta=3/4, r=1/5$.}

end{subfigure}

begin{subfigure}{0.45textwidth}

    includegraphics[width=linewidth]{long_pneumonic2.jpg}

    caption{Transient loops of the infected and susceptible population 

    changes.}

end{subfigure}

begin{subfigure}{0.45textwidth}

    includegraphics[width=linewidth]{long_pneumonic3.jpg}

    caption{The population of susceptible individuals and infected 

    individuals over a period of 1500 days post-vaccination.

    $alpha=0.000015, beta=0.0027, delta=.002, sigma=1/3, Delta=3/4, 

    r=1/5$.}

end{subfigure}

begin{subfigure}{0.45textwidth}

    includegraphics[width=linewidth]{long_pneumonic4.jpg}

    caption{[A graph showing the rise and decrease of pneumonic plague 

    victims leading to increasing amounts of infected with each recurrence 

    post-vaccination.}

end{subfigure}

caption{Graphs comparing and contrasting the same parameters examining the 

dynamics of the susceptible and infected populations pre and post 

vaccinations.}

end{figure}

end{document}

You wrote,

I keep getting errors

You didn't mention which errors you are getting, but I can only assume that they are caused by the line

begin{subfigure}[0.45textwidth]

at the start of the first subfigure environment. Change this line to

begin{subfigure}{0.45textwidth}

i.e., replace the square brackets with curly braces, and the immediate problem should be fixed. (Note that the other three begin{subfigure}{0.45textwidth} directives are already correct.) By the way, I'm assuming that your documents loads the subcaption package, not the obsolete and deprecated subfigure package.

In addition to fixing the syntax error, you may also want to "spruce up" the appearance of the figure. E.g., increase the horizontal separation between the subfigures, increase the space between the two rows of subfigures, and switch from full justification to centering for the captions of the four subfigures.

documentclass[demo]{article} % remove 'demo' option in real document

usepackage{graphicx,subcaption,ragged2e}

begin{document}



begin{figure}

captionsetup[subfigure]{justification=Centering}



begin{subfigure}[t]{0.45textwidth}

    includegraphics[width=textwidth]{long_pneumonic.jpg}

    caption{Pre-vaccination susceptible and infected population. $alpha=0.000015$, $beta=0.0027$, $delta= 0.002$, $sigma=1/3$, $Delta=3/4$, $r=1/5$.}

end{subfigure}hspace{fill} % maximize horizontal separation

begin{subfigure}[t]{0.45textwidth}

    includegraphics[width=linewidth]{long_pneumonic2.jpg}

    caption{Transient loops of the infected and susceptible population changes.}

end{subfigure}



bigskip % more vertical separation

begin{subfigure}[t]{0.45textwidth}

    includegraphics[width=linewidth]{long_pneumonic3.jpg}

    caption{The population of susceptible individuals and infected individuals over a period of 1500 days post-vaccination.

    $alpha=0.000015$, $beta=0.0027$, $delta=0.002$, $sigma=1/3$, $Delta=3/4$, 

    $r=1/5$.}

end{subfigure}hspace{fill} % maximize horizontal separation

begin{subfigure}[t]{0.45textwidth}

    includegraphics[width=linewidth]{long_pneumonic4.jpg}

    caption{A graph showing the rise and decrease of pneumonic plague victims leading to increasing amounts of infected with each recurrence post-vaccination.}

end{subfigure}



caption{Graphs comparing and contrasting the same parameters examining the  dynamics of the susceptible and infected populations pre and post  vaccinations.}



end{figure}

end{document}