Knitr: R package check error, object 'opts_chunk' not found

put library(knitr) before this opts_chunk$set(cache = TRUE, fig.path = "DFSurveyImages/", dev = "pdf")

You have to load the knitr library first, try this:

```{r setoptions, echo=FALSE}
library(knitr)
opts_chunk$set(cache = TRUE, fig.path = "DFSurveyImages/", dev = "pdf")```