In order to glue tide height (or tide current) onto each fish position observation:
1: Convert dates & times to POSIXct (do it all in GMT to avoid DST issues!). 2: Consider using NOAA tide data, available as 6 minute interval time series http://tidesandcurrents.noaa.gov/api/ . Luke Miller has functions for scraping their website ( http://lukemiller.org/index.php/2011/02/accessing-noaa-tide-data-with-r/ ) or I have a function: https://drive.google.com/file/d/0B-vmKFnoibOpVzRXNWxTZkthSm8/edit?usp=sharing 3: Convert dates to POSIXct, then data to ts. 4: Linearly interpolate the tide data to the times of your fish position. 5: glue tide data to fish data. 6: Use cut() or more complex computations to make your categorical tide status factor. I hope that this helps... Tom 2 On Tue, Mar 11, 2014 at 3:28 PM, Stacy Bierwagen <[email protected]>wrote: > Hello Listers, > > I am tracking home ranges of herbivorous reef fish and I have an extremely > large data set that includes 300,000 time-stamped lat/long coordinates. I > would like to assign a rank number to date/time in order to test position > of fish versus tidal level. I only have only taken tide level 4x/day so I > would like to create a function that ranks my temporal lat/long data as > presence/absence (0/1) of high tide or low tide to see if this > environmental factor significantly affects movement by using T-testing. I > am not sure how I would go about making a loop or incrementing an "i" value > to represent this in R. Should I first assign a numerical value to the > date/time before I try to quantify this? > > I included headers of the data I am looking at below if this helps. > > Stacy Bierwagen > > TIDE DATA > date time tidal height > days since day 0 time as 24h fraction h since day 0 > days since day 0 tidal height > 6/1/2013 4:13 0.33 > 0 0.175694444 4.216666667 > 0.175694444 0.33 > 6/1/2013 11:05 1.31 > 0 0.461805556 11.08333333 > 0.461805556 1.31 > 6/1/2013 14:31 1.04 > 0 0.604861111 14.51666667 > 0.604861111 1.04 > 6/1/2013 21:25 1.66 > 0 0.892361111 21.41666667 > 0.892361111 1.66 > 6/2/2013 4:49 0.1 > > TEMPORAL DATA: > Date TimeGMT DTHI DTConvertHI TConvertHI Frequency Signal Gain (dB) > Latitude Longitude 6/14/2013 23:52:52.336 06142013 23:52:52.336 06142013 > 13:52:52.336 13:52:52.000 63 86 0 21.43267 -157.791 6/14/2013 > 23:52:50.295 06142013 > 23:52:50.295 06142013 13:52:50.295 13:52:50.000 63 90 0 21.43267 -157.791 > 6/14/2013 23:52:38.051 06142013 23:52:38.051 06142013 13:52:38.051 > 13:52:38.000 63 88 0 21.43267 -157.791 6/14/2013 23:52:37.032 06142013 > 23:52:37.032 06142013 13:52:37.032 13:52:37.000 63 86 0 21.43267 -157.791 > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-ecology mailing list > [email protected] > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > -- ------------------------------------------- Tom Philippi, Ph.D. Quantitative Ecologist & Data Therapist Inventory and Monitoring Program National Park Service [email protected] http://science.nature.nps.gov/im/monitor [[alternative HTML version deleted]] _______________________________________________ R-sig-ecology mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
