R help - Oct 2009 - field names as function parameters

Hi,

I am passing a data frame and field name to a function. I've figured out how
I can create the formula based on the passed in field name, but I'm
struggling to create a vector based in that field.

for example if I hard code with the actual field name

Y = df$Target, everything works fine.

but if I use the passed in parameter name, it doesn't give me what I want,

Y = df$mytarget


Here is the function,

# trying to pass field name to a function
logistictest <- function(df,mytarget)
{

#library for AUC calculation
library(caTools)

#build logistic model
mytarget <- deparse(substitute(mytarget)) 
myformula <- paste(mytarget," ~ .")
myformula <- deparse(substitute(myformula)) 
logistic_reg <- glm(myformula , data=df,
family=binomial(link="logit"))
print("model build OK")

#score up
scores <- predict(logistic_reg, type="response", df)
print("model scored OK")

#calc AUC
Y = df$mytarget

auc <- colAUC(scores,Y)
print("auc calculated OK")

}

logistictest(df=trainset,mytarget=Target)


[1] "model build OK"
[1] "model scored OK"
Error in as.vector(x, mode) : invalid 'mode' argument

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Hi,

I think this is a case where you should use the ?"[[" extraction
operator rather than "$",

d = data.frame(a=1:3)
mytarget = "a"
d[[mytarget]]


HTH,

baptiste

2009/10/11 tdm <philb at philbrierley.com>:
>
> Hi,
>
> I am passing a data frame and field name to a function. I've figured
out how
> I can create the formula based on the passed in field name, but I'm
> struggling to create a vector based in that field.
>
> for example if I hard code with the actual field name
>
> Y = df$Target, everything works fine.
>
> but if I use the passed in parameter name, it doesn't give me what I
want,
>
> Y = df$mytarget
>
>
> Here is the function,
>
> # trying to pass field name to a function
> logistictest <- function(df,mytarget)
> {
>
> #library for AUC calculation
> library(caTools)
>
> #build logistic model
> mytarget <- deparse(substitute(mytarget))
> myformula <- paste(mytarget," ~ .")
> myformula <- deparse(substitute(myformula))
> logistic_reg <- glm(myformula , data=df,
family=binomial(link="logit"))
> print("model build OK")
>
> #score up
> scores <- predict(logistic_reg, type="response", df)
> print("model scored OK")
>
> #calc AUC
> Y = df$mytarget
>
> auc <- colAUC(scores,Y)
> print("auc calculated OK")
>
> }
>
> logistictest(df=trainset,mytarget=Target)
>
>
> [1] "model build OK"
> [1] "model scored OK"
> Error in as.vector(x, mode) : invalid 'mode' argument
>
> --
> View this message in context:
http://www.nabble.com/field-names-as-function-parameters-tp25838606p25838606.html
> Sent from the R help mailing list archive at Nabble.com.
>
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