R help - Oct 2009 - passing field name parameter to function

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/passing-field-name-parameter-to-function-tp25840014p25840014.html
Sent from the R help mailing list archive at Nabble.com.

You need to understand how accessing elements of a dataframe happen,
especially the '[[' operator (?"[[")

x <- function(dataFrame, name) dataFrame[[name]]

On Sat, Oct 10, 2009 at 9:27 PM, tdm <philb at philbrierley.com>
wrote:
>
> 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/passing-field-name-parameter-to-function-tp25840014p25840014.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

You code is not reproducible.

Take a look at this much simpler example:

 > a
   x y xx xxx
1 1 4  8  12
2 2 5  9  13
3 3 6 10  14
4 4 7 11  15
5 1 4  8  12
6 2 5  9  13
7 3 6 10  14
8 4 7 11  15

 > funct <- function(df, colnm) print(df[, colnm])

 > funct(a, "xx")
[1]  8  9 10 11  8  9 10 11
#----------
 > fortune(106)

If the answer is parse() you should usually rethink the question.
    -- Thomas Lumley
       R-help (February 2005)
#-----------
Further simple example:

(use dput(a) to produce the structure object:)


a <- structure(list(x = c(1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L), y = c(4L,
5L, 6L, 7L, 4L, 5L, 6L, 7L), xx = c(8L, 9L, 10L, 11L, 8L, 9L,
10L, 11L), xxx = c(12L, 13L, 14L, 15L, 12L, 13L, 14L, 15L)), .Names =  
c("x",
"y", "xx", "xxx"), row.names = c(NA, -8L), class =
"data.frame")

lmfunct <- function(df, idvar, dvar) lm( as.formula( paste(dvar, " ~  
", idvar, sep="") ), data=df)
lmfunct(a, "x", "y")

####---------------------------
Call:
lm(formula = as.formula(paste(dvar, " ~ ", idvar, sep =
"")),     data
= df)

Coefficients:
(Intercept)            x
           3            1

-- 
david

On Oct 10, 2009, at 9:27 PM, tdm wrote:
>
> 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/passing-field-name-parameter-to-function-tp25840014p25840014.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

On Oct 10, 2009, at 9:27 PM, tdm wrote:
>
> 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)
A further comment. There is no object "Target" (or if there is, it is
created by code that you have not included).  There is only a name  
"Target" for a list element in the object "df". The
formalism df
$Target is really syntactic window dressing for df$"Target" and it  
only works because $ is designed to extract named elements from within  
an object that is visible to to the interpreter at this level. (Sorry  
for imprecise language, but that what noobs like me end up resorting  
to.)
>
>
> [1] "model build OK"
Actually that is not tested. I suspect that if you wrote:   
print(logistic_reg) ...  it would be empty.
> [1] "model scored OK"
> Error in as.vector(x, mode) : invalid 'mode' argument
> -- 
David Winsemius, MD
Heritage Laboratories
West Hartford, CT