Use R-kernel if only this kernel is used.

[BoPeng]

We use a SoS kernel to allow the use of

• markdown-kernel for inline expressions
• other kernels for code blocks in other languages

For Rmarkdown documents that do not use these two features, it makes sense to create a regular Jupyter notebook with only a R kernel.

[albertostefanelli]

This would allow a user to port the converted notebook to a Google Collaboraty compatible format

[BoPeng]

Whereas 2 (other kernels) is not frequently used, 1 (inline expression) is. How do you handle inline expressions using only the R kernel?

[BoPeng]

The new behavior is that an R notebook will be generated if there is no inline expression and non-R code block, and --execute is not used.