I get an error when I put an imaginary number in a column of a table with column specifier S (from siunitx package)

Question

Using the siunitx package. I have a table with column specifier S if I then put an imaginary number in it comes up with a compile time error:

! siunitx error: "table-partial-number"
!
! No space reserved for a complex on line 20.
!
! See the siunitx documentation for further information.
...
| The number in the current table cell contains a complex part,
| but you did not reserve any space to print it:
| it will be missing in the output.

It sounds like I need to enter in some optional argument to make this work but I don't know what that is from reading the manual.

Here's some code (remove the i in the left column to make to compile):

\documentclass{article}
\usepackage{siunitx}
\usepackage{booktabs}


\begin{document}


\begin{table}
   \centering
   \sisetup{table-alignment=center}
   \begin{tabular}{ S S S S }
   \toprule
      \multicolumn{3}{c}{things} & \\
          a             &  b             &  c             & {related things}\\
   \midrule
          1             &  1             &  1             &   1    \\
          2             &  1             &  2             &   4    \\
          3i             &  2             &  3             &  18    \\
          4             &  2             &  4             &  32    \\
      \bottomrule
   \end{tabular}
\end{table}

\end{document}

Answer 1

(More of a comment, but converted to an answer as there is not a better one.)

Currently "this won't work". I added complex numbers to support certain edge-case uses where you see, for example, imaginary frequencies. Dealing with these in tables has not exactly been a priority: there are a large number of possible alignment cases that I'm not too keen on taking on. I've always imagined that in a table, the complex part would in any case have a column to itself and be divide by i, for example Imaginary frequency/i cm$^-1$.