R - Markdown avoiding package loading messages

```{r results='hide', message=FALSE, warning=FALSE}
library(RJSONIO)
library(AnotherPackage)
```

see Chunk Options in the Knitr docs

You can use include=FALSE to exclude everything in a chunk.

```{r include=FALSE}
source("C:/Rscripts/source.R")
```

If you only want to suppress messages, use message=FALSE instead:

```{r message=FALSE}
source("C:/Rscripts/source.R")
```