[R] trouble with append() in a for loop

[Sarah Goslee]

Hi,

Look at this line:

cross.val.error<-append(cross.val.error.temp,value.temp)

at each iteration you're overwriting cross.val.error with
cross.val.error.temp and value.temp

You probably actually need something like

cross.val.error.temp <- append(cross.val.error.temp,value.temp)
print(cross.val.error.temp)

But this is far from a small reproducible example, so you could need
something else entirely.

Sarah

On Fri, Jun 1, 2012 at 2:23 PM, Benjamin Caldwell
<btcaldwell at berkeley.edu> wrote:
> Hello all,
> *
> *
> I'm having some difficulty, and I think the problem is with how I'm using
> append() nested inside a for loop. The data are:
>
> y,x
> 237537.61,873
> 5007.148438,227
> 17705.77306,400
> 12396.64369,427
> 228703.4021,1173
> 350181.9752,1538
> 59967.79376,630
> 140322.7774,710
> 42650.07251,630
> 5382.858702,264
> 34405.82429,637
> 92261.34614,980
> 144927.1713,1094
> 362998.7355,1420
> 203313.6442,1070
> 168861.649,930
> 214306.5266,1040
> 201804.5193,1000
> 108426.1988,820
> 181651.8748,980
> 53675.45849,775
> 43068.82972,563
> 92393.35158,805
> 93305.0618,740
> 107308.4761,840
> 139056.5446,775
> 15411.81924,420
> 16104.80991,390
> 25629.07578,502
> 37121.23438,461
> 29711.42749,565
> 33400.49145,510
>
> and the code is:
>
> xy<-read.csv(xy.csv)
> x<-xy$x
> y<-xy$y
> cross.val.error.temp<-numeric(0)
> b<-c(1:length(x))
>
> for(i in b){
> frame.val.temp<-data.frame(x,y)
> frame.val<-frame.val.temp[-i,]
> yt<-frame.val$y
> xt<-frame.val$x
> temppow.val<-lm(log(yt)~log(xt))
> tempint.val<-summary(temppow.val)$coefficients[1,1] #intercept of power
> function
> tempslope.val<-summary(temppow.val)$coefficients[2,1]
> nls.model.val<-nls(yt~exp(intercept)*((xt)^slope),
> start=list(intercept=tempint.val, slope=tempslope.val))
> prediction.cross.val<-((exp(intercept.nls))*((x[i])^slope.nls))
> value.temp<-(prediction.cross.val-y[i])/y[i]
> cross.val.error<-append(cross.val.error.temp,value.temp)
> cross.val.error
> print(cross.val.error)
> }
> cross.val.error
>
> print() shows the values that I'm looking for, but I must be doing
> something wrong with append because the call to cross.val.error just
> returns the last value that the for loop returns. Would anyone be willing
> to show me how to correct my mistake?
>
> As an aside, if anyone cares to explain how to make this work using lapply
> instead of a for loop, I'm very interested.
>
> Many thanks for looking.
>
> *Ben Caldwell*
>



-- 
Sarah Goslee
http://www.functionaldiversity.org