# Missing number treated as zero in subfigure caption

What number am I missing the moment I want a subcaption for my subfigure it tells me I'm missing a number for some reason. The error also disappears if I remove the roman counter option.

\documentclass[a4paper,UKenglish]{article}
\usepackage{graphicx}
\usepackage{caption}
\usepackage{subcaption}
\renewcommand{\thesubfigure}{\roman{counter}}
\begin{document}
asdfasdf

\begin{figure}
\centering
\begin{subfigure}[b]{0.45\textwidth}
\includegraphics[scale=0.5]{example-grid-100x100pt}
\end{subfigure}
\begin{subfigure}[b]{0.45\textwidth}
\includegraphics[scale=0.5]{example-grid-100x100pt}
\end{subfigure}
\caption{Caption}

\end{figure}

\end{document}

\end{document}

• are you using both packages subfigure and subcaption -- have a look here -- tex.stackexchange.com/questions/19946/… – js bibra Dec 13 '20 at 6:05
• @jsbibra I didn't load the subfigure package though is there a way to stop it from loading? – Hao S Dec 13 '20 at 6:07
• Does your code example actually lead to the error message? – Dr. Manuel Kuehner Dec 13 '20 at 6:11
• @Dr.ManuelKuehner sorry I accidentally deleted a line \usepackage{graphicx} fixed now – Hao S Dec 13 '20 at 6:19
• Please make the code compilable without pic1.png etc, see tex.stackexchange.com/questions/231738. Do you know that you can format the code in your question (in the editor)? – Dr. Manuel Kuehner Dec 13 '20 at 6:20

You use wrong name for subfigure caption's number. Instead of counter it must be subfigure (see @Dr. Manuel Kuehner answer).I guess that you like to obtain the following result:

Complete MWE is:

\documentclass[a4paper,UKenglish]{article}
\usepackage{graphicx}
\usepackage{caption}
\usepackage{subcaption}
\renewcommand\thesubfigure{\roman{subfigure}}

\usepackage{lipsum} % added for generation of dummy text

\begin{document}
\lipsum[11]

\begin{figure}[ht]
\centering
\begin{subfigure}[b]{0.45\textwidth}
\centering
\includegraphics[scale=0.5]{example-grid-100x100pt}
\caption{first subfigure}
\end{subfigure}
\hfil
\begin{subfigure}[b]{0.45\textwidth}
\centering
\includegraphics[scale=0.5]{example-grid-100x100pt}
\caption{second subfigure}
\end{subfigure}
\caption{Caption}
\end{figure}

\end{document}

• +1: Very good! @HaoS Please accept this answer. – Dr. Manuel Kuehner Dec 13 '20 at 8:09