Double spaced document with exceptions

Question

I have to set the line space among my thesis double. So I use the following commands at preamble

\setlength{\parindent}{1em}
\setlength{\parskip}{1em}
\renewcommand{\baselinestretch}{1.8}

However, the line space at the following items should be untouched and regular:

• Captions
• Footnotes
• Bibliography entries of more than one line

What commands should I add?

Answer 1

setspace provides 4 commands intended for use in the preamble:

• \singlespacing
• \doublespacing
• \onehalfspacing
• \setstretch{<factor>}

Alternatively, the package options singlespacing, onehalfspacing or doublespacing may be used in place of the first three. singlespacing is default.

In addition, a further option nodisplayskipstretch may be set to prevent extra spacing around display environments.

For use in the body of the document, the package provides 4 environments:

• \begin{singlespace}...\end{singlespace}
• \begin{singlespace*}...\end{singlespace*}
• \begin{onehalfspace}...\end{onehalfspace}
• \begin{doublespace}...\end{doublespace}
• \begin{spacing}{<factor>}...\end{spacing}

Although the preamble commands will work in the document body, they are not designed for use there and will result in sub-optimal spacing in many cases. This is because the environments do more than simply switch the stretch using the \...ing commands.

For example, here's the definition of singlespace:

\newenvironment{singlespace}{% from setspace.sty
  \vskip \baselineskip
  \setstretch {\setspace@singlespace}%
  \vskip -\baselineskip
}{%
  \par
}

In contrast, here's the definition of \singlespacing:

\newcommand{\singlespacing}{% from setspace.sty
  \setstretch {\setspace@singlespace}%  normally 1
  \vskip \baselineskip  % Correction for coming into singlespace
}

While \setstretch {\setspace@singlespace} is the same in both definitions, the adjustments differ in other ways because the environment makes adjustments specifically required in the case of line spacing changes within a document.

The difference between singlespace and singlespace* is in the specific adjustments made. Here's singlespace*:

\newenvironment{singlespace*}{% from setspace.sty
  \setstretch {\setspace@singlespace}%
  \vskip -\baselineskip
}{%
  \vskip -0.5\baselineskip
}

As can be seen, the vertical spacing changes differ between the two environments and between both environments and \singlespacing.

Similar differences exist for the other preamble command/corresponding environment pairs.

In general, therefore, it is best to use the environments intended for use within the body within the body. In some cases, the differences will not change the output because, for example, there's a page break at the start and end of the changed line-spacing anyway. But the differences will matter in other cases so it is best to use the environments as a routine within the document body unless there is some special reason to do otherwise.

\documentclass...
...
\usepackage{setspace}
\setstretch{1.8}
...
\begin{document}
...
\begin{singlespace}
<bibliography commands go here>
\end{singlespace}
...
\end{document}

Answer 2

Don't modify the low-level parameter \baselinestretch directly. Instead, insert the following instructions in the preamble:

\usepackage{setspace}
\setstretch{1.8}

Or, use a spacing environment with an argument of 1.8, in the body of the document:

\begin{spacing}{1.8}
 ...
\end{spacing}

Just let the spacing environment end before the start of the bibliography.

An MWE:

\documentclass{article}
\usepackage{lipsum} % filler text
\usepackage{setspace}
\begin{document}
\begin{spacing}{1.8}
\lipsum*[1]\footnote{\lipsum*[2]}  % automatic single-spacing in footnotes

\end{spacing}

\begin{thebibliography}{9}

\bibitem{z} xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx 

\end{thebibliography}
\end{document}