latexmk engine + knitr (Mac OS)

latexmk code

#There isn't a built-in engine for knitr, but it's easy to make one. 
#The engine itself is just a shell script. Here's my belt-and-braces version that believes you are on a unix machine 
#but doubts that your paths are set up properly:

        #!/bin/bash
        export PATH=$PATH:/usr/texbin:/usr/local/bin
        
        if (Rscript -e "library(knitr); knit('$1')") then
          latexmk -pdf "${1%.*}"
        fi
        
#In brief, this tries to run the R code in double quotes on the first argument ($1) which is the name of the .Rnw file. 
#If this succeeds then the transformation from latex+R to pure latex must have been successful, so we can call latexmk on the 
#resulting file. latexmk runs latex, then biber, then latex, then latex again, then... until all the citations are cited, 
#the contents are tabled, and all the cross references are happy again.