[R] Calculating distance between spatial points

[Nicolas Korber]

Hello,
to call each variable separately, you can coerce your sp object back to a
dataframe. The code below should to the job:

DF.utm <- as.data.frame(SP.utm)
long.diff<-diff(DF.utm$Long)

Nicolas


Tim Clark wrote:
> 
> 
> Dear List,
> 
> I am trying to determine the speed an animal is traveling on each leg of a
> track.  My data is in longitude and latitude, so I am using the package
> rgdal to convert it into a spatial points data frame and transform it to
> UTM.  I would then like to find the difference between successive
> longitudes and latitudes, find the euclidean distance between points, and
> compute the speed of the animal on each leg.
> 
> My problem is that once I convert the lat and long into a spatial points
> data frame I can not access the lat and long individually.  As far as I
> know I need to convert them in order to transform the lat and long to UTM. 
> Is there a way I can call each variable separately in the sp dataframe? 
> My code with example data is below.  Any suggestions would be appreciated.
> 
>   library(rgdal) 
>   date.diff<-(20,30,10,30)
>   Long<-c(-156.0540 ,-156.0541 ,-156.0550 ,-156.0640)
>   Lat<-c(19.73733,19.73734,19.73743,19.73833) 
>    
>   SP<-data.frame(Long,Lat)  
>   SP<-SpatialPoints(SP,proj4string=CRS("+proj=longlat +ellps=WGS84"))
>   SP.utm<-spTransform(SP, CRS("+proj=utm +zone=4 +ellps=WGS84")) 
>   
>   long.diff<-diff(SP.utm$Long)
>   lat.diff<-diff(SP.utm$Lat)
>   
>   d=(long.diff^2+lat.diff^2)^.5
>   speed=d/date.diff
> 
> 
> Aloha,
> 
> Tim
> 
> 
> 
> Tim Clark
> Department of Zoology 
> University of Hawaii
> 
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> 
> 

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