How can I change figure caption label?

Question

I am using revtex4-1 for a Physical Review Letter. Typically when a figure is made, the caption starts out FIG. 1. <text>. I am creating a supplementary file and I would like it to say FIG. S1. <text>. How can I change that?

Answer 1

A global modification to \thefigure of the form

\renewcommand{\thefigure}{S\arabic{figure}}

would suffice (in your document preamble). Alternatively, if you only want to modify the figure number representation in the caption only (since you might not be referencing it as part of "supplementary figures"), you could use

\makeatletter
\renewcommand{\fnum@figure}{\figurename~S\thefigure}
\makeatother

The former is preferred, since it makes more sense.