[Rd] R CMD check tells me 'no visible binding for global variable ', what does it mean?

[Michael Dewey]

When I run R CMD check on a package I have recently started work on I 
get the following:

* checking R code for possible problems ... NOTE
addlinear: no visible binding for global variable 'x'

I appreciate that this is only a NOTE and so I assume is R's 
equivalent of 'This is perfectly legal but I wonder whether it is 
really what you intended' but I would like to understand it.

In the relevant function addlinear the following function is defined locally:

    orfun <- function(x, oddsratio) {1/(1+1/(oddsratio * (x/(1-x))))}

and then used later in curve

       curve(orfun(x, exp(estimate)), from = 0.001, to = 0.999, add = TRUE)

These are the only occurrences of 'x'.

Is it just telling me that I have never assigned a value to x? Or is 
it more sinister than that? As far as I can tell the function does 
what I intended.


Michael Dewey
http://www.aghmed.fsnet.co.uk