[R] Need script to create new waypoint

[Mike Marchywka]

> Now I need to change this data set into one with waypoints at regular intervals: for example 2 
 
I guess your question is about algorithm ideas for making up data due to
unspecified percrived need. Anything you can specify completely should be easy
to code in R, maybe a bash script, or c++ or java, not sure the Excel was intended
for arbitrary code. Generally the choice of how you manufacture data 
would be dictated by the percieved need. If you can elaborate on the "need"
maybe someone can help you pick an approach to making things up.
 
There is a sig list for geo problems that may know your requirement better,
 
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
 
and of course if your need is to replicate prior work in the field, you
can contact authors directly for questions about what they did.
 
If your question is about how R can handle time series with pre-packaged
things, there is quite a bit notably "zoo" and "ts" which
I think should come up with "?zoo" and "?ts"
 
http://www.google.com/search?hl=en&safe=off&q=R+ts+regular+time+intervals
 
also try "interpolation" search. 
 
> library(zoo)
> ?zoo
> ?ts
>
 
 

----------------------------------------
> From: antie66 at hotmail.com
> To: r-help at r-project.org
> Date: Tue, 14 Jun 2011 11:55:57 +0000
> Subject: [R] Need script to create new waypoint
>
>
> Dear help-list members,
>
> I am a student at Durham University (UK) conducting a PhD on spatial representation in baboons. Currently, I'm analysing the effect of sampling interval on home range calculations.
>
> I have followed the baboons for 234 days in the field, each day is represented by about 1000 waypoints (x,y coordinates) recorded at irregular time intervals. Consecutive waypoints in this raw data set have an average distance interval of 5 meters an average time interval of 23 seconds (but when baboons were stationary the time interval could be much larger - e.g. waypoint 7 below).This raw data set needs to become a data set with waypoints at regular intervals and thus, 'new' waypoints have to be 'created'. Eventually, I want to use seven different time intervals: 2, 5, 10, 15, 30, 45 and 60 minute intervals. I have tried in Excel, but I am not managing it. I have some experience with R, and although I can 'read' quite complicated scripts, I am unable to write them, so I would very much appreciate any help anybody would be willing to offer me.
>
>
>
> My current data set has 9 columns (in csv / excel file):
> x coordinate, y coordinate, year, month, day, record, time interval (duration between this waypoint and the previous) (hh:dd:ss), summed time intervals, distance interval (m)
>
>
> EXAMPLE (24th of april 2007)
>
> (wp1) x1, y1, 2007, 7, 24, 1, 00:00:00, 00:00:00, 0
> (wp2) x2, y2, 2007, 7, 24, 2, 00:00:23, 00:00:23, 2
> (wp3) x3, y3, 2007, 7, 24, 3, 00:00:50, 00:00:73, 3
> (wp4) x4, y4, 2007, 7, 24, 4, 00:01:20, 00:02:33, 5
> (wp5) x5, y5, 2007, 7, 24, 5, 00:00:03, 00:02:36, 1
> (wp6) x6, y6, 2007, 7, 24, 6, 00:00:12, 00:02:48, 2
> (wp7) x7, y7, 2007, 7, 24, 7, 00:05:45, 00:08:33, 2
>
> Now I need to change this data set into one with waypoints at regular intervals: for example 2 minutes = 120 seconds >> 2 minutes after the first waypoint (x1,y1) the baboons would be somewhere between WP3 and WP4 (at WP3 sum duration is 73 seconds and after WP4 sum duration is 153 seconds), and so this is where I would like a new waypoint created. Note that there are time intervals which will be so large that multiple 'new' waypoints have to be made / copied (e.g. WP 7 for a 2 minute interval).
>
> Three ways of calculating the new coordinates for this new waypoint from very precise to not so precise (in order of preference) are:
>
>
>
> 1) Basing the new waypoint coordinates on the relative 'time distance' to each waypoint of the two surrounding waypoints (therewith assuming a constant movement during the time interval). The 'time distance' bewteen WP3 and WPnew is (120-73) 47 seconds and the 'time distance' between WPnew and WP4 is (153-120) 33 seconds (whereas total time interval between WP3 and WP4 is 80 seconds). WPnew (with coordinates Xnew,Ynew) should then be located at 80/33*100=41.25% from WP3: Xnew = X3 + (X4-X3)*41.25% and Ynew= Y3 + (Y4-Y3)*41.25%
>
>
> 2) Calculate the average location (average of x3,y3 and x4,y4), at which to create a new waypoint at 2 minutes.
>
>
> 3) A simpler alternative is that the location of the 'closer waypoint in time', in this example WP 4, (WP4: 153-120=33 versus WP3: 120-73=47) could be copied as being the new location.
>
>
>
> I hope I explained my query so that it makes sense to you. I realize I am asking a 'big' question and apologize for this - the software programs I have thorough knowledge of (ArcGIS, excel, Mapsource), are all unable to solve this problem. I would be very grateful for any advice or suggestions.
>
> Best wishes,
> Louise
>
> [[alternative HTML version deleted]]
>
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