knitr - Using an R variable before the code chunk in which the variable was created

Question

I would like to include an R calculation in the abstract. The R calculation is at the bottom of document, so when I compile the Rnw file I get an error.

Here is a minimal example:

documentclass{article}
egin{document}

egin{abstract}
    This paper... and we got a mean of Sexpr{mean.data}.
end{abstract}

<<>>=
data <- c(1,2,3,4,5)
mean.data <- mean(data)
@

end{document}

Answer 1

Well you obviously need to move the definition of something being used before it is being used, not after. So try this instead:

documentclass{article}
egin{document}

<<>>=
data <- c(1,2,3,4,5)
mean.data <- mean(data)
@

egin{abstract}
    This paper... and we got a mean of Sexpr{mean.data}.
end{abstract}

end{document}

Chunks can occur just about everywhere, including before egin{document}.