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

[Rui Barradas]

Hello,

The following should be faster. It preallocates a vector of length nrows 
instead of extending 'a' on every iteration.

a2 <- character(nrows)
for(b in 1:nrows)
{
	c= ColChange(data[b,1],data[b,2],data[b,3:6],2)
	a2[b]=c
}
all.equal(c(a), a2)


As for the use of apply, I'm getting errors but the way to call it would 
be, after changing ColChange in order to correct some of the errors, 
(changed: ncol to NCOL and colnames to names)


ColChange2 <- 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 = names(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 = names(Vals)[cols]
     }
   }
   }
   return(Result)
}
#################################################

apply(data, 1, function(x) ColChange2(x[1], x[2], x[3:6], 2) )
Error in ColChange2(x[1], x[2], x[3:6], 2) : object 'Result' not found


So there's some debugging to be done.
Anyway, the revised loop should be much faster.


Hope this helps,

Rui Barradas

Em 23-03-2013 11:08, Camilo Mora escreveu:
> 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/
>
> ______________________________________________
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