[R] Help finding the mode and maximum for a specified 'window' of time series data

[jim holtman]

This will give you an idea of how you might want to approach the problem:

> sample <-cbind((1:20)*.25,c(1,1,1,2,2,3,3,3,4,5,6,4,4,3,3,3,2,1,1,1))
> sample
      [,1] [,2]
 [1,] 0.25    1
 [2,] 0.50    1
 [3,] 0.75    1
 [4,] 1.00    2
 [5,] 1.25    2
 [6,] 1.50    3
 [7,] 1.75    3
 [8,] 2.00    3
 [9,] 2.25    4
[10,] 2.50    5
[11,] 2.75    6
[12,] 3.00    4
[13,] 3.25    4
[14,] 3.50    3
[15,] 3.75    3
[16,] 4.00    3
[17,] 4.25    2
[18,] 4.50    1
[19,] 4.75    1
[20,] 5.00    1
> # range of timing
> s.r <- range(sample[,1])
> # create groupings for 1 minute intervals
> s.cut <- seq(from=floor(s.r[1]), to=ceiling(s.r[2]), by=1)
> s.cut
[1] 0 1 2 3 4 5
> # split the data
> s.split <- split(sample[,2], cut(sample[,1], s.cut))
> s.split
$`(0,1]`
[1] 1 1 1 2

$`(1,2]`
[1] 2 3 3 3

$`(2,3]`
[1] 4 5 6 4

$`(3,4]`
[1] 4 3 3 3

$`(4,5]`
[1] 2 1 1 1

> # determine maximum in interval
> sapply(s.split, max, na.rm=TRUE)
(0,1] (1,2] (2,3] (3,4] (4,5]
    2     3     6     4     2
> # mode (maximum # of occurances)
> sapply(s.split, function(x) {
+     .tab <- table(x)
+     as.numeric(names(.tab)[which.max(.tab)])
+ })
(0,1] (1,2] (2,3] (3,4] (4,5]
    1     3     4     3     1
>
>


On Sun, Jun 15, 2008 at 12:10 PM, Staples, Angela Dawn
<adstaple at indiana.edu> wrote:
> I am relatively new to R, so apologize up front for my long question,
> particularly if there is too much or too little information.
>
> I have a large time series data set where each subject's behavior was
> originally coded on .25s intervals for 3min task. I am trying to determine
> if the findings are different depending on the coding interval (i.e. Compare
> .25s to 1s to 5s to 10s).
>
> I also need to see if it makes a difference if I use the maximal value
> within the interval or the modal value within the interval. In other words,
> I do not need the average value.
>
> Here a sample of my data with time as the first column:
>
> sample <-cbind((1:20)*.25,c(1,1,1,2,2,3,3,3,4,5,6,4,4,3,3,3,2,1,1,1))
>
>      [,1] [,2]
>  [1,] 0.25    1
>  [2,] 0.50    1
>  [3,] 0.75    1
>  [4,] 1.00    2
>  [5,] 1.25    2
>  [6,] 1.50    3
>  [7,] 1.75    3
>  [8,] 2.00    3
>  [9,] 2.25    4
> [10,] 2.50    5
> [11,] 2.75    6
> [12,] 3.00    4
> [13,] 3.25    4
> [14,] 3.50    3
> [15,] 3.75    3
> [16,] 4.00    3
> [17,] 4.25    2
> [18,] 4.50    1
> [19,] 4.75    1
> [20,] 5.00    1
>
> I need help returning the maximum and minimum of a specified "window" such
> that the function/loop/etc would return:
>
> maximum (window=4, or 1s) would be (2, 3, 6, 4, 2)
> mode (window=4, or 1s) would be (1, 3, 4, 3, 2)
>
> Given the coding conventions in this research area, I need the values to be
> from adjacent, as opposed to overlapping, windows. There are likely to be
> situations where there is no clear mode (1,1,2,2). In those cases it would
> be fine to have 1.5 or 2 returned, but not NA. The data file is in the long
> format with each subject having 720 rows of data. I've tried playing with
> the row indices, but I cannot figure out how to 'move' the window.
>
> I would appreciate any help/suggestions. Since I'm new to this, the
> suggestion doesn't have to be pretty, I just need it to work.
>
> Sincerely,
>
> Angela
>
> ~~~~~~~~~~~~~~~~~~~~~~
> Angela Staples
> Doctoral Candidate
> Psychological and Brain Sciences
> Indiana University
> 1101 E. 10th St.
> Bloomington, IN 47405
> http://www.indiana.edu/~batessdl/
>
> The plural of anecdote is not data.
> ~ Roger Brinner
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

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