[R] Error with custom function in apply: ”Error in FUN(newX[, i], ...) : unused argument(s) (newX[, i])”

[Camilo Mora]

Hi everyone,

I wonder if I can get your help using a custom function in apply.

Imagine the following dataframe called "data":

LowLim		HighLim	        A1	A2	A3	A4
4		6		3	4	5	6
4		6		4	5	5	6
2		3		1	4	2	3
2		3		NA	NA	NA	NA

We have created a custom function (see below) that takes the values in  
a given row between columns A1 to A4 to see if they are outside the  
limits in the same row set by columns LowLim and HighLim, if at least  
x consecutive values are outside, the function returns the column name  
of the first column in that series. If no value is outside, the  
function returns the name of the last column and if there are NAs, the  
function returns NA.

So in the example above, the function return the following results:

Considering 2 consecutive values outside the limits:
A4
A4
A1
NA

Considering 1 value outside the limits:
A1
A4
A1
NA

The problem we have is that our dataframe has over 1.2 million rows.  
So right now we are using a loop (see below), which work fine by  
entering the values of each row in our function but it will take  
several days to complete. The idea is to see if we can use our  
function with apply. Basically,

data$Results<-apply(data,1, ColChange, LowLim=data[1],  
HighLim=data[2], Vals=data[3:6], NumConsecOut=2)

But we get the following error: ”Error in FUN(newX[, i], ...) : unused  
argument(s) (newX[, i])”

Any idea about this error or an alternative way to obtain the results  
we look for.

Thank you very much,

Camilo

################# Our function is: #######################
ColChange <- function(LowLim, HighLim, Vals, NumConsecOut) {
   cols <- ncol(Vals)
   yr_init = 0
   k = 0
   for (i in 1:cols){
     val = Vals[i]
     if (is.na(val)){
       Result="NA"
       next
     } else {
     if (val<LowLim||val>HighLim){
       if (yr_init==0) {
         yr_init = colnames(Vals)[i]
         k = k + 1
       } else {
         k = k + 1
       }
       if (k==NumConsecOut){
         Result=yr_init
         break
       }
     } else {
       yr_init=0
       k=0
     }
      if (yr_init==0){
       Result=colnames(Vals)[cols]
     }
   }
   }
   return(Result)
}
#################################################



#######Our loop is:###############################
nrows=nrow(data)

a=c()

for(b in 1:nrows)
{
c= ColChange(data[b,1],data[b,2],data[b,3:6],2)
a=rbind(a,c)
}
#################################################


Camilo Mora, Ph.D.
Department of Geography, University of Hawaii
Currently available in Colombia
Phone:   Country code: 57
          Provider code: 313
          Phone 776 2282
          From the USA or Canada you have to dial 011 57 313 776 2282
http://www.soc.hawaii.edu/mora/