R markdown df_print options

Question

I have a R markdown document in RStudio, where a data.table is printed. I want to set the data frame print options to control printed number of rows and columns, as described here.

Here is a minimal example .Rmd file:

---
output: 
  html_document: 
    fig_height: 8
    fig_width: 10
    df_print: paged
---

```{r}
knitr::opts_chunk$set(echo = FALSE)
cars
```

Where/how do I set the rows.print option?

I've tried this:

---
output: 
  html_document: 
    fig_height: 8
    fig_width: 10
    df_print: paged
    rows.print: 25
---

which doesn't work (still at default 10 rows), and this:

```{r}
knitr::opts_chunk$set(echo = FALSE, rows.print=25)
cars
```

which also doesn't work.

Answer 1

The knitr::opts_chunk$set(rows.print=25) option setting applies only to subsequent chunks, hence in the minimal example it doesn't change the setting.

The option can be set in the chunk as shown in chunk1 or globally in opts_chunk for subsequent chunks.

```{r chunk1, rows.print=15}
knitr::opts_chunk$set(echo = TRUE, rows.print=25)
cars #15 rows printed
```

```{r chunk2}
cars #25 rows printed
```