[R] Ensure parameter is a string when passed within an lapply & called function runs a 'substitute' on it

[David Winsemius]

> On May 9, 2016, at 2:39 PM, Andrew Clancy <nite at achren.org> wrote:
> 
> Hi, 
> 
> I’m trying to solve what looks like the same issue as stack overflow article, but within an lapply:
> http://stackoverflow.com/questions/18939254/cant-use-a-variable-as-an-argument-but-can-use-its-value


It would be helpful if you could articulate the issue.

> 
> I’ve replicated the issue with partialPlot below in ‘testFunc’. The lines up to the final print can’t change (including the substitute). In the first call it prints out ‘X1’ correctly, in the second it prints out ‘var’. I’ve tried eval, quote etc as the article suggests. Any ideas?
> 
> numObs  <- 10
> numVars <- 6
> dataSet    <- data.frame(replicate(numVars,rnorm(numObs)))
> # partialPlot(x = model, pred.data = dataSet, x.var = 'X1', plot = F) 

I'm assuming that the comment character is actually something that was inserted in hte process of stripping hte HTML from this posting.

It throws an error when removed:

Error in partialPlot(x = model, pred.data = dataSet, x.var = "X1", plot = F) : 
  object 'model' not found

> 

> testFunc <- function(x, pred.data, x.var, plot=F) {
>   x.var <- substitute(x.var)

Try changing to eval(x.bar)

>   # print(paste('is.character(x.var)', is.character(x.var), 'is.name(x.var)', is.name(x.var)))

>   xname <- if (is.character(x.var)) x.var else {
>     if (is.name(x.var)) deparse(x.var) else {
>       eval(x.var)
>     }
>   }
>   print(xname)
>   # print(head(pred.data[,xname]))
> }
> 
> vars <- names(dataSet)[[1]]
> testFunc(x = model, pred.data = dataSet, x.var = local(vars), plot = F)

Returns:
[1] "is.character(x.var) TRUE is.name(x.var) FALSE"
[1] "X1"
[1]  0.8704543 -0.4421564 -0.6725336 -1.3096399 -1.0531335 -0.4979650


> 
> lapply(vars, function(var) {
>   # print(paste('var', var))
>   testFunc(x = model, pred.data = dataSet, x.var = var, plot = F)
> })

Retruns:
[1] "var X1"
[1] "is.character(x.var) TRUE is.name(x.var) FALSE"
[1] "X1"
[1]  0.8704543 -0.4421564 -0.6725336 -1.3096399 -1.0531335 -0.4979650
[[1]]
[1]  0.8704543 -0.4421564 -0.6725336 -1.3096399 -1.0531335 -0.4979650


> 
> 	[[alternative HTML version deleted]]

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-- 

David Winsemius
Alameda, CA, USA