Setting work directory in knitr using opts_chunk$s

问题:

My R project is structured like a package with directories /R, /vignettes, /data etc. In one of my Rmd docs in /vignettes I source a script which in located in /R. Inside this script I use read.csv() to load a file located in inst/extdata/.
The problem now is that by default the working directory inside the Rmd file is the directory where the file is located. Let's call it /Users/Me/Docs/Proj/vignettes. However in order for the R script to run the working directory needs to be the project's main directory (/Users/Me/Docs/Proj).
I tried to change the working directory in the Rmd file using knitr::opts_chunk$set(root.dir = normalizePath(".."). However apparently this doesn't change the working directory since if I call getwd() after it the output is still /Users/Me/Docs/Proj/vignettes whereas knitr::chunk_opts$get("root_dir") returns /Users/Me/Docs/Proj.

Here is a minimal example Rmd file:

```{r}
getwd()  # returns 'Users/Me/Docs/Proj/vignettes'
knitr::opts_chunk$set(root.dir = normalizePath(".."))  # should change the working directory to 'Users/Me/Docs/Proj'
getwd()  # again returns 'Users/Me/Docs/Proj/vignettes'
knitr::opts_chunk$get("root.dir")  # returns 'Users/Me/Docs/Proj'
```

I am using RStudio Version 0.99.435. Here is my session Info:

R version 3.2.0 (2015-04-16)  
Platform: x86_64-apple-darwin14.3.0 (64-bit)  
Running under: OS X 10.10.3 (Yosemite)  

locale:
[1] de_DE.UTF-8/de_DE.UTF-8/de_DE.UTF-8/C/de_DE.UTF-8/de_DE.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

loaded via a namespace (and not attached):
[1] htmltools_0.2.6 tools_3.2.0     yaml_2.1.13     rmarkdown_0.6.1 digest_0.6.8   

Any help is kindly appreciated. If you need more info post a comment to the question. Thanks in advance!

回答1:

It is knitr::opts_knit instead of knitr::opts_chunk.

回答2:

As Yihui has pointed out in his answer the mistake was simply that I used opts_chunk$set() instead of opts_knit$set().
However it might be worth noting that the change of the working directory affects not the current but only the next chunk. So e. g. if you want to load data relative to the new working directory do that in the following chunk.

回答3:

Where you have an R project with nested subfolders, so that the .Rproj and .Rmd files are located in different folders, you can use the command rprojroot::find_rstudio_root_file() to find and set the working directory to the Project's main folder during Kniting (instead of the folder containing the rMarkdown code file).

So at a minimum use the following:

```{r setup}

knitr::opts_knit$set(root.dir = rprojroot::find_rstudio_root_file())

```

inside the setup chunk.

See also Automatically finding the path of current R project in R Studio and https://support.rstudio.com/hc/en-us/community/posts/220826588-Working-directory-in-R-Notebooks.

回答4:

Some details on implementation of setting work directory by root.dir =.
Although there already are some awesome answers by Yihui and Tommy. I still got stuck in setting work directory. So I am trying to make a complete answer here.

1. From knitr documentation:

Knitr’s settings must be set in a chunk before any chunks which rely on those settings to be active. It is recommended to create a knit configuration chunk as the first chunk in a script with cache = FALSE and include = FALSE options set. This chunk must not contain any commands which expect the settings in the configuration chunk to be in effect at the time of execution.

2. My code example:

In my case, the .Rproj and .Rmd files are located in the same folder.

```{r setup, include=FALSE, cache = FALSE}
require("knitr")
## setting working directory
opts_knit$set(root.dir = "~/Documents/R/Example")
```