[R] 'class(.) == **' [was 'Call to a function']

[Steven Yen]

Thanks Davis. But actually, the line is legitimate:

    if (inherits(wt,what="character")) wt<-data[,wt]

because, coming down with wt being characters, the part wt<-data[,wt] 
then picks up variables data$wt. The call

    wmean(mydata,wt="weight")

actually goes OK. I was hoping to figure out a way to fix the wmean 
routine some how so that I can call with

    wmean(mydata,wt=weight)

Good to know there is a better way to initialize the vector Mean and and 
a better list command. Thank you!

On 6/26/2015 2:39 AM, David Winsemius wrote:
>
> On Jun 25, 2015, at 7:48 PM, Steven Yen wrote:
>
>> Thanks to all for the help. I have learned much about "inherit" and "class". I like to know about one additional option, and that is to use a calling parameter without the quotation marks, similar to the linear regression syntax:
>>
>> lm(data=mydata,weights=wt)
>>
>> Below is a simple set of codes to calculate weighted means with generated data in data frame "mydata". As annotated below, I like the following call to work (without the quotations):
>>
>> wmean(mydata,wt=weight)
>
> Let's start with the call. If you are to execute this,  then names `mydata` and `weight` each must have a value.
>
>>
>> Thank you!
>> ----
>>
>> mydata<-matrix(1:20,ncol=2)
>
> OK. There is a value having been assigned to `mydata`
>
>> mydata<-cbind(mydata,runif(10,0,1))
>
> And now augmented.
>
>> colnames(mydata)<-c("y","x","weight")
>
> And a names attribute added for its columns.
>
>> mydata<-as.data.frame(mydata)
>>
>> wmean <- function(data,wt){
>>   if (inherits(wt,what="character")) wt<-data[,wt]
>>   wt<-wt/mean(wt)
>
> Here's the problem. If `wt` was of mode "character", then you cannot divide it by a number, since the RHS will be evaluated first. You really should read the error messages!
>
> Perhaps you meant:
>
> wt <-  data[, wt]/mean(data[ , wt]
>
> But if you did, then it's rather confusing (but possible) to assign the value to the same name as the column of the matrix.
>
>
>>   Mean<-NULL
>
> Why do that? If you remove it from the workspace then you cannot assign a value using indexed assignment as you apparently intend to do. Should have been
>
> Mean <- numeric( ncol(data) )
>
>
>>   for (i in 1:ncol(data)){
>>     Mean[i] <- sum(data[,i]*wt)/sum(wt)
>
> There is a bit of a confusion here. `wt` started out as a character value. I guess you could do this.
>
>>   }
>>   list("Mean: ",Mean)
>
> Wrong syntax for lists. Suspect you want 	
>
>     list(Mean=Mean)
>
>
>> }
>> wmean(mydata,wt="weight") # This works
>> wmean(mydata,wt=weight)   # <= Like this to work
>
> So were you planning to execute this first?
>
> weight="weight" #?
>

-- 
Steven Yen
My e-mail alert:
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