{example} fails unless {theorem} exists in document

[JeffreyRacine]

Greetings,

Using the minimal example (index.Rmd below), the following demonstrates the problem. If the environment e.g. ```{theorem} does not exist somewhere (it can precede or proceed ```{example}) in the document then the following error is thrown:

output file: bookdown-demo.knit.md

! LaTeX Error: Environment example undefined.

Error: Failed to compile bookdown-demo.tex. See bookdown-demo.log for more info.
Execution halted

Exited with status 1.

If you compile the code below all is well, remove ```{theorem} and it fails. Thanks!

--- 
title: "A Minimal Book Example"
author: "Yihui Xie"
date: "`r Sys.Date()`"
site: bookdown::bookdown_site
output: bookdown::gitbook
documentclass: book
bibliography: [book.bib, packages.bib]
biblio-style: apalike
link-citations: yes
github-repo: rstudio/bookdown-demo
description: "This is a minimal example of using the bookdown package to write a book. The output format for this example is bookdown::gitbook."
---

```{theorem}
Test
```

```{example}
Test
```

[yihui]

Should be fixed now. Thanks for the report!

[JeffreyRacine]

Thank you!

[JeffreyRacine]

Greetings,   One thing arises – typically there is paragraph space before the example, but none occurs here… see attached… if space is expected it would be great to have this patch…   Jeff

[yihui]

Could you reply the issue on Github? The email attachment won't be sent here automatically.

[JeffreyRacine]

Certainly...

[JeffreyRacine]

Following up with code... there is a space in the code... note that html output is great, just not the PDF...

For example, to test the hypothesis that $\rho_1=0$ and $\rho_2=0$, we could use the $\mathcal{Q}_{lb}$ statistic given by $T(T+2)(\hat\rho_1^2/(T-1)+\hat\rho_2^2/(T-2))$ and test the hypothesis by comparing this statistic with a critical value taken from a $\chi^2_{(2)}$ distribution (i.e. a $\chi^2$ random variable having two degrees of freedom such as the 5% level critical value `r format(qchisq(0.95,df=2),digits=3)` obtained via `qchisq(0.95,df=2)`).

```{example}

Let's consider a simple example where you are given $\hat\rho_1$ and $\hat\rho_2$ and $T$ (the length of the series) and then manually conduct individual and joint tests for white noise and report the outcome of the test.

Supposed that we wished to test $H_0\colon\rho_1=0$ based on $T=100$ realizations of a time series, and we computed $\hat\rho_1=0.15121$, $Var[\hat\rho_1]=1/100=.01$, hence $Z=\hat\rho_1/\sqrt{Var[\hat\rho_1]}=0.15121/.1=1.5121$. We would fail to reject the null at all conventional levels. You might ask yourself exactly what this failure to reject the null means in the current context.

If we wished to test $H_0\colon\rho_2=0$ and we computed $\hat\rho_2=0.069739$, $Var[\hat\rho_2]=(1+2\times 0.15121^2)/100=  0.0104573$, hence $Z=\hat\rho_2/\sqrt{Var[\hat\rho_2]}=0.069739/ 0.102260=0.68197$. Again, we would fail to reject the null at all conventional levels.

If we wished to test $H_0\colon\rho_1=0\cap\rho_2=0$, then $\mathcal{Q}_{lb}=100(100+2)[0.15121^2/(100-1)+0.069739^2/(100-2)]$ which equals $10200[0.022865/99+ 0.0048635/98]$ which equals $2.86194$. For $\alpha=0.05$, $\chi^2_{2,1-\alpha}=5.99147$ so again we would fail to reject the null.

```

[yihui]

That is a separate issue. You can add these lines of LaTeX code to your preamble to increase the spacing: https://github.com/rstudio/bookdown/blob/4e94c8d499/inst/examples/latex/preamble.tex#L92-L98 If you don't know how, here is the documentation: https://bookdown.org/yihui/bookdown/yaml-options.html (use the in_header option).

Source of the solution: http://tex.stackexchange.com/q/85400/9128

[JeffreyRacine]

Thanks!

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