Plotting multiple animal tracks against Date/Time

Sorry for posting this questions twice, but my previous question was accidentally sent unfinished. 

Dear list,

I would like to create a time series plot in which the paths of several individuals are stacked above each other, with the x-axis being the total observation period of three years ( 1.1.2004 to 31.12.2007) and the y-axis being  some defined range[min,max].

My data consist of Date/Time information and the paths of 45 individual as the distance from the location of release. An example data set for 2 individuals is given below.The observation period and frequency of observations varies between individuals.

I believe stackplot() may be able to do this task, but I am not sure how to handle the variable time period and frequency of observations for different individuals. Could someone advise if stackplot() is suitable or if there is a better approach or package ?

Thank you very much for your time,

Juliane


Individual 1

Date                    Distance [m]

2005-07-18 22:05:15 1815.798
2005-07-18 22:06:35 1815.798
2005-07-18 22:08:33 1815.798
2005-07-18 22:09:49 1815.798
2005-07-18 22:12:50 1815.798
2005-07-18 22:16:26 1815.798

Individual 2

Date                          Distance [m]
2006-08-18 09:53:20      0.0
2006-08-18 09:59:07      0.0
2006-08-18 10:09:20      0.0
2006-08-18 10:21:14   100.5

Dr. Juliane Struve
Imperial College London
Department of Life Sciences
Ascot, Berkshire,
SL5 7PY, UK