Assuming your polyline is defined by two vectors, one for the x
coordinates, one for the y coordinates, you can try the following
library(NISTunits)
polyangles <- function(xV,yV) {
stopifnot( (length(xV)==length(yV)) && (length(xV) >= 3))
v <- function(i) { c( xV[i]-xV[i-1], yV[i]-yV[i-1])}
vlen <- function(v) { sqrt(sum(v*v)) }
lV <- rep(NA_real_,length(xV))
for ( i in 2:(length(xV)-1) )
lV[i] <- acos( sum(v(i)*v(i+1))/(vlen(v(i))*vlen(v(i+1))) )
angleV <- NISTunits::NISTradianTOdeg(lV)
angleV
}
# example
x <- c(0:3)
y <- c(0,0,1,1)
polyangles( x, y )
# NA 45.0 45.0 NA
Note, I have included the NA's at the beginning and end of the polyline as
a reminder that there is no angle defined there.
HTH,
Eric
On Tue, Jan 30, 2018 at 4:34 PM, Jeff Newmiller <jdnewmil at
dcn.davis.ca.us>
wrote:
> A polyline by definition has many angles, so your question is ill-formed.
> And this is a question about math, not R, so is off topic here. I suggest
> reading Wikipedia.
> --
> Sent from my phone. Please excuse my brevity.
>
> On January 29, 2018 11:10:02 PM PST, javad bayat <j.bayat194 at
gmail.com>
> wrote:
> >Dear R users
> >I am trying to find a formula to calculate the angle of a polyline. Is
> >there a way to do this?
> >Many thanks.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/
> posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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I like to use complex numbers for 2-dimensional geometry. E.g.,> polyAngles2function (xV, yV) { stopifnot((length(xV) == length(yV)) && (length(xV) >= 3)) z <- complex(re = xV, im = yV) c(NA, diff(Arg(diff(z))), NA) # radians, positive is counter-clockwise }> x <- c(0:3) > y <- c(0,0,1,1) > polyAngles2(x,y) / pi * 180[1] NA 45 -45 NA Bill Dunlap TIBCO Software wdunlap tibco.com On Tue, Jan 30, 2018 at 7:09 AM, Eric Berger <ericjberger at gmail.com> wrote:> Assuming your polyline is defined by two vectors, one for the x > coordinates, one for the y coordinates, you can try the following > > library(NISTunits) > polyangles <- function(xV,yV) { > stopifnot( (length(xV)==length(yV)) && (length(xV) >= 3)) > v <- function(i) { c( xV[i]-xV[i-1], yV[i]-yV[i-1])} > vlen <- function(v) { sqrt(sum(v*v)) } > > lV <- rep(NA_real_,length(xV)) > for ( i in 2:(length(xV)-1) ) > lV[i] <- acos( sum(v(i)*v(i+1))/(vlen(v(i))*vlen(v(i+1))) ) > angleV <- NISTunits::NISTradianTOdeg(lV) > angleV > } > > # example > x <- c(0:3) > y <- c(0,0,1,1) > polyangles( x, y ) > > # NA 45.0 45.0 NA > > Note, I have included the NA's at the beginning and end of the polyline as > a reminder that there is no angle defined there. > > HTH, > Eric > > > On Tue, Jan 30, 2018 at 4:34 PM, Jeff Newmiller <jdnewmil at dcn.davis.ca.us> > wrote: > > > A polyline by definition has many angles, so your question is ill-formed. > > And this is a question about math, not R, so is off topic here. I suggest > > reading Wikipedia. > > -- > > Sent from my phone. Please excuse my brevity. > > > > On January 29, 2018 11:10:02 PM PST, javad bayat <j.bayat194 at gmail.com> > > wrote: > > >Dear R users > > >I am trying to find a formula to calculate the angle of a polyline. Is > > >there a way to do this? > > >Many thanks. > > > > ______________________________________________ > > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide http://www.R-project.org/ > > posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/ > posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >[[alternative HTML version deleted]]
nice On Tue, Jan 30, 2018 at 7:05 PM, William Dunlap <wdunlap at tibco.com> wrote:> I like to use complex numbers for 2-dimensional geometry. E.g., > > > polyAngles2 > function (xV, yV) > { > stopifnot((length(xV) == length(yV)) && (length(xV) >= 3)) > z <- complex(re = xV, im = yV) > c(NA, diff(Arg(diff(z))), NA) # radians, positive is counter-clockwise > } > > x <- c(0:3) > > y <- c(0,0,1,1) > > polyAngles2(x,y) / pi * 180 > [1] NA 45 -45 NA > > > > Bill Dunlap > TIBCO Software > wdunlap tibco.com > > On Tue, Jan 30, 2018 at 7:09 AM, Eric Berger <ericjberger at gmail.com> > wrote: > >> Assuming your polyline is defined by two vectors, one for the x >> coordinates, one for the y coordinates, you can try the following >> >> library(NISTunits) >> polyangles <- function(xV,yV) { >> stopifnot( (length(xV)==length(yV)) && (length(xV) >= 3)) >> v <- function(i) { c( xV[i]-xV[i-1], yV[i]-yV[i-1])} >> vlen <- function(v) { sqrt(sum(v*v)) } >> >> lV <- rep(NA_real_,length(xV)) >> for ( i in 2:(length(xV)-1) ) >> lV[i] <- acos( sum(v(i)*v(i+1))/(vlen(v(i))*vlen(v(i+1))) ) >> angleV <- NISTunits::NISTradianTOdeg(lV) >> angleV >> } >> >> # example >> x <- c(0:3) >> y <- c(0,0,1,1) >> polyangles( x, y ) >> >> # NA 45.0 45.0 NA >> >> Note, I have included the NA's at the beginning and end of the polyline as >> a reminder that there is no angle defined there. >> >> HTH, >> Eric >> >> >> On Tue, Jan 30, 2018 at 4:34 PM, Jeff Newmiller <jdnewmil at dcn.davis.ca.us >> > >> wrote: >> >> > A polyline by definition has many angles, so your question is >> ill-formed. >> > And this is a question about math, not R, so is off topic here. I >> suggest >> > reading Wikipedia. >> > -- >> > Sent from my phone. Please excuse my brevity. >> > >> > On January 29, 2018 11:10:02 PM PST, javad bayat <j.bayat194 at gmail.com> >> > wrote: >> > >Dear R users >> > >I am trying to find a formula to calculate the angle of a polyline. Is >> > >there a way to do this? >> > >Many thanks. >> > >> > ______________________________________________ >> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see >> > https://stat.ethz.ch/mailman/listinfo/r-help >> > PLEASE do read the posting guide http://www.R-project.org/ >> > posting-guide.html >> > and provide commented, minimal, self-contained, reproducible code. >> > >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide http://www.R-project.org/posti >> ng-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> > >[[alternative HTML version deleted]]