Hi everyone,
i have a matrix of points and want to calculate the direction and length of each
vector between the points.
I can easily calculate the length with dist(testdata), but is their a function
that returns a matrix of the direction of the vectors between points (angles
0-360?)?
testdata <- matrix(1:8, nrow=4, ncol=2,
dimnames=list(c("A","B","C","D"),
c("x","y"))
Le samedi 28 mars 2009 ? 16:06 +0000, Wanja Mathar a ?crit :> Hi everyone, > > i have a matrix of points and want to calculate the direction and length of each vector between the points. > > I can easily calculate the length with dist(testdata), but is their a function that returns a matrix of the direction of the vectors between points (angles 0-360?)? > > testdata <- matrix(1:8, nrow=4, ncol=2, > dimnames=list(c("A","B","C","D"), c("x","y"))?atan2 ; ?outer Emmanuel Charpentier
Thank you! I managed it with this function - for a data fram with x and y
coordinates:
anglefun<-function(x,y,unit="degrees")
{x.new<-outer(x,x,"-");
y.new<-outer(y,y,"-");angles<-atan2(x.new,y.new);diag(angles)<-NA;if(unit
== "degrees")
return(180*angles/pi)
if (unit == "radians")
return(angles)}
returns a matrix with the directions in degrees or radians and sets the angle
between the same point to NA
Emmanuel Charpentier schrieb:
Le samedi 28 mars 2009 ? 16:06 +0000, Wanja Mathar a ?crit :
Hi everyone,
i have a matrix of points and want to calculate the direction and length of each
vector between the points.
I can easily calculate the length with dist(testdata), but is their a function
that returns a matrix of the direction of the vectors between points (angles
0-360?)?
testdata <- matrix(1:8, nrow= ncol=2,
dimnames=st(c("A","B","C","D"),
c("x","y"))
?atan2 ; ?outer
Emmanuel Charpentier