[R] Trouble Passing a for loop variable (iteration #) to a data frame

[Galen Moore]

Thank you very much, Peter.  The " iter[i] = x[i]" solution worked
perfectly.

Galen

-----Original Message-----
From: Peter Langfelder [mailto:peter.langfelder at gmail.com] 
Sent: Monday, April 25, 2011 17:07
To: galen.a.moore at gmail.com
Cc: r-help at r-project.org
Subject: Re: [R] Trouble Passing a for loop variable (iteration #) to a data
frame

You need to index the variable iter: instead of iter = x[i], say

iter[i] = x[i].

But a better solution is to simply say

iter = x

at the beginning and don't update it in the loop.

The way your code is written, iter just holds the last x[i], and the last
x[i] at the end of each loop is 4.

Peter

On Mon, Apr 25, 2011 at 3:29 PM, Galen Moore <galen.a.moore at gmail.com>
wrote:
> Greetings -
>
>
>
> I am working on a piece of code to simulate vehicle times in and out 
> in each of a number of parking spaces.  At this stage, my code 
> basically does what it is supposed to do but for the sequential number 
> of each new parking event for a given space (i.e., the index of the 
> loop variable).  Instead of passing the index of the loop variable 
> (iter) to the data frame, it passes the value of the total number of 
> iterations.  Eventually, the number of iterations (parking events in a 
> given space) will be determined by an
> rnorm() fcn, so I am not looking for a process that locks-in the 
> number of iterations.  The total eventual data set size is small-ish, 
> so I'm not worried about speed.
>
>
>
> I'm sure my problem lies somehow in my setup of the data frames and my
> rbind() fcns, but a great many attempts and several hours of searching 
> online have not yet brought success.
>
>
>
> Can you please suggest what I need to do to get the iteration # to 
> appear in the "iter" vector and therefore to the data frame?
>
>
>
> Many thanks,
>
>
>
> Galen
>
>
>
>
>
>> # fabdata3.r
>
>> # fabricate sample data
>
>>
>
>> #declare the mean duration
>
>> dur<-.04
>
>>
>
>> #declare the stdDev of the rnorm() fcn (duration)
>
>> varc<-.01
>
>>
>
>> sp<-numeric()
>
>> iter<-numeric()
>
>> ti<-numeric()
>
>> to<-numeric()
>
>> actdur<-numeric()
>
>> #newline<-data.frame(sp, iter, ti, to, actdur)
>
>> ds<-data.frame(sp, iter, ti, to, actdur)
>
>>
>
>> # BEGIN OUTER LOOP
>
>> for (sp in c(1:3)) {
>
> +
>
> +            ct<-1
>
> +            # BEGIN INNER LOOP
>
> +
>
> +            x <- seq(1, 4, by=1)
>
> +            for (i in seq(along=x)) {
>
> +
>
> +                         if (i == 1)   {
>
> +                          ti[1]<-((.333333+rnorm(1, dur, varc)))
>
> +                          to[1]<-((ti[1]+rnorm(1, dur, varc)))
>
> +                          actdur[1]<-(to[1]-ti[1])
>
> +                          iter<-x[1]
>
> +
>
> +                          }
>
> +
>
> +                         else {
>
> +                         # set subsequent time-ins to prev to + a 
> + rand#
>
> +                         ti[i]<-((to[i-1]+rnorm(1, dur, varc)))
>
> +                         # calculate each event's time-out
>
> +                         to[i]<-((ti[i]+rnorm(1, dur, varc)))
>
> +                         # calculate each event's actual duration
>
> +                         actdur[i]<-(to[i]-ti[i])
>
> +                         iter<-x[i]
>
> +
>
> +                         }
>
> +                          spStep<-paste("sp Value is ", sp)
>
> +                          print(spStep)
>
> +                          iterStep<-paste("iter Value is ", iter)
>
> +                          print(iterStep)
>
> +
>
> +                         newrow<-data.frame(sp, iter, ti, to, actdur)
>
> +                         ct=ct+1
>
> +                  }  #END INNER LOOP
>
> +                  ds<-rbind(ds, newrow)
>
> +             }
>
> [1] "sp Value is  1"
>
> [1] "iter Value is  1"
>
> [1] "sp Value is  1"
>
> [1] "iter Value is  2"
>
> [1] "sp Value is  1"
>
> [1] "iter Value is  3"
>
> [1] "sp Value is  1"
>
> [1] "iter Value is  4"
>
> [1] "sp Value is  2"
>
> [1] "iter Value is  1"
>
> [1] "sp Value is  2"
>
> [1] "iter Value is  2"
>
> [1] "sp Value is  2"
>
> [1] "iter Value is  3"
>
> [1] "sp Value is  2"
>
> [1] "iter Value is  4"
>
> [1] "sp Value is  3"
>
> [1] "iter Value is  1"
>
> [1] "sp Value is  3"
>
> [1] "iter Value is  2"
>
> [1] "sp Value is  3"
>
> [1] "iter Value is  3"
>
> [1] "sp Value is  3"
>
> [1] "iter Value is  4"
>
>>             print(ds)
>
>   sp iter        ti        to     actdur
>
> 1   1    4 0.3600055 0.4123550 0.05234955
>
> 2   1    4 0.4343887 0.4640804 0.02969170
>
> 3   1    4 0.5240268 0.5622272 0.03820032
>
> 4   1    4 0.5945877 0.6436489 0.04906118
>
> 5   2    4 0.3694827 0.4166405 0.04715775
>
> 6   2    4 0.4609841 0.4968517 0.03586767
>
> 7   2    4 0.5357721 0.5735439 0.03777185
>
> 8   2    4 0.6207077 0.6512799 0.03057217
>
> 9   3    4 0.3801887 0.4122605 0.03207179
>
> 10  3    4 0.4440002 0.4916171 0.04761685
>
> 11  3    4 0.5380228 0.5791549 0.04113214
>
> 12  3    4 0.6087923 0.6291451 0.02035284
>
>> # END OUTER LOOP
>
>>
>
>
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>
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