Variable space between numbers and errors/uncertainties in mathmode?

Question

I am relatively new to Latex and did not find an answer to the following problem: I am writing a thesis using the book class. The text contains many numbers including their plus/minus uncertainties. I normally type them as following:

Example 1: $-1.123 \pm 0.123$
Example2: $(1.2 \pm 0.1) \times \num{e-2}$

However, the space in between the plus/minus sign and the numbers left and right changes, depending on where in the text it appears. Sometimes it is without any space and sometimes there is quite some space. What am I doing wrong? From scientific articles I know that this should be consistent throughout the whole text?

I know, in the first example I could write: -1.123 $\pm$ 0.123. In that case the space will be added each time, but the minus sign looks ugly then. Any advice? Thanks for your help!

Answer 1

Use siunitx:

\documentclass{article}
\usepackage{amsmath}
\usepackage{siunitx}

\sisetup{separate-uncertainty}

\begin{document}

\num{-1.123 \pm 0.123}

\num{1.2 \pm 0.1 e-2}

\end{document}

The parentheses are mandatory.

With this code we see that the spaces are not expanded:

\documentclass{article}
\usepackage{amsmath}
\usepackage{siunitx}

\sisetup{separate-uncertainty}

\begin{document}

\num{-1.123 \pm 0.123} abc

\leavevmode\hbox spread 20pt{\num{-1.123 \pm 0.123} abc}

\num{1.2 \pm 0.1 e-2} abc

\leavevmode\hbox spread 20pt{\num{1.2 \pm 0.1 e-2} abc}

\end{document}