coords[insiders,] Gabor
On Sat, Apr 22, 2006 at 02:45:24PM -0400, Jian Zhang wrote: > I want to get the actual value of the points in the circle. > Can you tell me how to get them? > Thanks! > > >insiders > [1] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE > [13] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE > [25] FALSE FALSE FALSE FALSE FALSE TRUE TRUE FALSE FALSE FALSE FALSE FALSE > [37] FALSE FALSE FALSE FALSE FALSE TRUE FALSE TRUE FALSE FALSE TRUE FALSE > [49] FALSE TRUE > > > > On 4/22/06, Gabor Csardi <[EMAIL PROTECTED]> wrote: > > > >Fine, than just check every point like suggested below. > >(whether (c1-x)^2+(c2-y)^2 < r^2) > >and call 'symbols' to add the circle to the plot like this: > >symbols(c1, c2, circles=r, inches=FALSE, add=TRUE) > > > >For example, if coords is a two column matrix of the coordinates of the > >points: > > > >################################ > >coords <- matrix( runif(100), nc=2 ) > >c1 <- c2 <- 0.5 > >r <- 0.2 > > > >insiders <- apply(coords, 1, > > function(co) (c1-co[1])^2+(c2-co[2])^2 < r^2) > >plot(coords) > >symbols(c1, c2, circles=r, inches=FALSE, add=TRUE) > >################################ > > > >'insiders' will be a logical vector telling whether the points are inside > >or > >outside the circle. > > > >Gabor > > > >On Sat, Apr 22, 2006 at 02:16:38PM -0400, Jian Zhang wrote: > >> Thanks! > >> There are many points in our plot. I want to choose the points which > >> distance to one point (e.g.(100,200)) is less than 10. > >> And I want to draw a circle (radinus=10). The centre of the circle is > >the > >> point (100,200). > >> > >> > >> On 4/22/06, Gabor Csardi <[EMAIL PROTECTED]> wrote: > >> > > >> >Hmmm, could you explain this a bit? > >> >You want to add a circle to a plot? See the examples in help(symbols) > >> > > >> >Or you want to calculate the coordinates of the points on a circle? > >> > > >> >t <- seq(0,2*pi,length=100) > >> >coords <- t(rbind( 10+sin(t)*2, 20+cos(t)*2)) > >> >plot(coords) > >> > > >> >Here (10,20) is the center of the circle, and 2 is its radius. > >> >If you set length to a bigger number you'll get smoother resolution. > >> > > >> >A points (x,y) is inside the circle if (c1-x)^2+(c2-y)^2 < r^2 > >> >(c1, c2) is the center of the circle, r is its radius. > >> > > >> >Gabor > >> > > >> >On Sat, Apr 22, 2006 at 01:42:46PM -0400, Jian Zhang wrote: > >> >> how to draw a circle (e.g. radius=10cm) of one point? > >> >> And how to choose these points in the circle? > >> >> Thanks! > >> >> > >> >> [[alternative HTML version deleted]] > >> >> > >> >> ______________________________________________ > >> >> [email protected] mailing list > >> >> https://stat.ethz.ch/mailman/listinfo/r-help > >> >> PLEASE do read the posting guide! > >> >http://www.R-project.org/posting-guide.html > >> > > >> >-- > >> >Csardi Gabor <[EMAIL PROTECTED]> MTA RMKI, ELTE TTK > >> > > > > >-- > >Csardi Gabor <[EMAIL PROTECTED]> MTA RMKI, ELTE TTK > > > >______________________________________________ > >[email protected] mailing list > >https://stat.ethz.ch/mailman/listinfo/r-help > >PLEASE do read the posting guide! > >http://www.R-project.org/posting-guide.html > > -- Csardi Gabor <[EMAIL PROTECTED]> MTA RMKI, ELTE TTK ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
