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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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>
>
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