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

Staples, Angela Dawn adstaple at indiana.edu
Sun Jun 15 18:10:06 CEST 2008

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