[kepler-users] passing a pathname as a Parameter or Constant in RExpression

[Hurlbert, Allen Hartley]

Hello all,

I'm using Kepler 2.2 on a Windows 7 machine with R 2.14.0.

Following some of the examples in the UserManual, I've tried creating a Parameter in which I specify a directory to which output should be written.

E.g.,

DataOutDir: "//bioark.bio.unc.edu/hurlbertallen/manuscripts/birdmigration/workflow/data"

I am using RExpression actors to manipulate data and then I try to write that data using something like

write.csv(output, paste(DataOutDir,"/output.csv",sep=""))

but Kepler doesn't seem to be treating DataOutDir as an R object which is how I was thinking about it.

I can see that if I create a Constant with the pathname as a string, and then port this directly into the RExpression actor that it works as expected. The trick is that I have lots of RExpression actors where I'd like to specify this pathname, and would prefer not having to add lots of unnecessary visual clutter to the workflow by adding extra ports and relations just to bring in the pathname everywhere its needed. Is there a simpler way?

Is my question any different if I'm talking about creating a Parameter that is an integer value (e.g. the year for which data will be subsetted), that I'd like to reference repeatedly in different RExpression actors? I guess I'm thinking of the Lotka-Volterra example where the model parameters are not explicitly linked by relations to the actual expressions. Can I create the equivalent of a Parameter that is universally visible to RExpressions?

I acknowledge that the phrasing of my question may reflect a complete misunderstanding of how Kepler works, and so I appreciate any and all feedback.

Thanks,
Allen
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