I am trying to use the reticulate package in a Rmd file. I first created a setup chunk as follows:

```
library(reticulate)
use_virtualenv("r-reticulate")
use_python("C:\\Python27")

```

Then I import `pandas`: 

```
#importing libraries
import pandas 

```

```
 ImportError: No module named pandas

Detailed traceback: 
  File "<string>", line 1, in <module>  

```

I have checked that pandas is already installed from the python command line. Why am I getting an import error here?