Example of conditional chunk evaluation depending on document output type

example-conditional-chunk-eval.Rmd

---
title: "Example of conditional chunk evaluation"
author: "Jesús M. Castagnetto"
date: "2019-05-30"
output:
  pdf_document:
    toc: true
    number_sections: true
  html_document:
    df_print: paged
    mathjax: null
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(
  echo = TRUE,
  warning = FALSE,
  message = FALSE)
```

# How to evaluate chunks depending on the document output

To get conditional chunk evaluation we make use of the functions `knitr::is_html_output()` and `knitr::is_latex_output()`.

We´ll create a simple plot:

```{r}
plot_iris <- ggplot2::ggplot(iris, ggplot2::aes(x = Sepal.Length, y = Sepal.Width)) +
  ggplot2::geom_point(ggplot2::aes(color = Species))
```

## The following chunk will be evaluated only if the output is HTML

And the code will generate an interactive plot using the `plotly` package.

```{r eval=(knitr::is_html_output())}
plotly::ggplotly(plot_iris)
```

## And the following, only if the output will be PDF

The code here will generate a regular plot

```{r eval=(knitr::is_latex_output())}
plot_iris +
  ggplot2::theme_minimal()
```

## And this one will appear in both

Just a simple table

```{r}
knitr::kable(head(iris, 5), booktabs = TRUE)
```