[R] can't find 'predict.loess' in a loop

[Stuart Leask]

Season's Greetings.

I am using 'predict' in a loop, but it is behaving unexpectedly, so I am more explicit and use 'predict.loess', and R says it can't find it. Even if I explicitly load the stats library, which is already in the search path.

Any ideas?
This is odd, because if I use RB & LB from a different dataset, it works fine...


Stuart

*********************************************************************
*************************
Original problem:

> j<-0                      # start an iteration counter
> while(j<30)               # (max 30 iterations)
+ 
+ {
+ 
+   lenRB<-length(RB)       # number of rows in original RB
+   lenLagRB<-(j+1):lenRB   # row numbers for 'lagged' RB
+   lenLagRB0<-1:(lenRB-j)  # row numbers for 'unlagged' RB
+   RBj<-RB[lenLagRB]       # create a 'lagged' RB of this length
+   LBj<-LB[lenLagRB]       # create a 'lagged' LB of this length
+   RB0<-RB[lenLagRB0]      # create an 'unlagged', shortened RB of this length
+   LB0<-LB[lenLagRB0]      # create an 'unlagged' LB of this length
+ 
+   cor.j<-cor(RBj,LB0)     # check RB lagged & LB have low correlation
+ if(abs(cor.j)<0.01)     # if so...
+ 
+   {
+ 
+ RELBj<-100*(RBj-LB0)/(RBj+LB0)  # ...generate index for lagged pair
+ RELB0<-100*(RB0-LB0)/(RB0+LB0)  # generate index for unlagged pair
+ 
+   Lag.lo <-loess(RBj~RELBj,span=sp, family=("symmetric"), degree=2) # close approx of lowess!
+   Real.lo<-loess(RB0~RELB0,span=sp, family=("symmetric"), degree=2)
+   Lag.pr <-predict(Lag.lo, data.frame(x=seq (-80,80,1)))  # predict for uniform index scale
+   Real.pr<-predict(Real.lo,data.frame(x=seq (-80,80,1)))
+ 
+   Diff.pr<-Real.pr-Lag.pr                                   # difference plot
+   lines (Diff.pr~seq(-80,80,1),pch=1,cex=0.25,col=1)
+ 
+ }
+ 
+ j<-j+1                   # increment counter and repeat
+ }
Error in model.frame.default(formula = Diff.pr ~ seq(-80, 80, 1), na.action = NULL) : 
  variable lengths differ (found for 'seq(-80, 80, 1)')
In addition: Warning messages:
1: 'newdata' had 161 rows but variable(s) found have 250 rows 
2: 'newdata' had 161 rows but variable(s) found have 250 rows 

****************************
Make it more explicit I want to use predict.loess:

> j<-0                      # start an iteration counter
> while(j<30)               # (max 30 iterations)
+ 
+ {
+ 
+   lenRB<-length(RB)       # number of rows in original RB
+   lenLagRB<-(j+1):lenRB   # row numbers for 'lagged' RB
+   lenLagRB0<-1:(lenRB-j)  # row numbers for 'unlagged' RB
+   RBj<-RB[lenLagRB]       # create a 'lagged' RB of this length
+   LBj<-LB[lenLagRB]       # create a 'lagged' LB of this length
+   RB0<-RB[lenLagRB0]      # create an 'unlagged', shortened RB of this length
+   LB0<-LB[lenLagRB0]      # create an 'unlagged' LB of this length
+ 
+   cor.j<-cor(RBj,LB0)     # check RB lagged & LB have low correlation
+ if(abs(cor.j)<0.01)     # if so...
+ 
+   {
+ 
+ RELBj<-100*(RBj-LB0)/(RBj+LB0)  # ...generate index for lagged pair
+ RELB0<-100*(RB0-LB0)/(RB0+LB0)  # generate index for unlagged pair
+ 
+   Lag.lo <-loess(RBj~RELBj,span=sp, family=("symmetric"), degree=2) # close approx of lowess!
+   Real.lo<-loess(RB0~RELB0,span=sp, family=("symmetric"), degree=2)
+   Lag.pr <-predict.loess(Lag.lo, data.frame(x=seq (-80,80,1)))  # predict for uniform index scale
+   Real.pr<-predict.loess(Real.lo,data.frame(x=seq (-80,80,1)))
+ 
+   Diff.pr<-Real.pr-Lag.pr                                   # difference plot
+   lines (Diff.pr~seq(-80,80,1),pch=1,cex=0.25,col=1)
+ 
+ }
+ 
+ j<-j+1                   # increment counter and repeat
+ }
Error: could not find function "predict.loess"

****************

> search()
 [1] ".GlobalEnv"        "nshd"             
 [3] "package:foreign"   "package:stats"    
 [5] "package:graphics"  "package:grDevices"
 [7] "package:utils"     "package:datasets" 
 [9] "package:methods"   "Autoloads"        
[11] "package:base"     
> ?predict.loess

... Confirms that predict.loess is in the path, and can be accessed.
Only not within the loop?
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