[R] Smooth contour of a map

[Duncan Murdoch]

On 17/05/2011 8:24 AM, Pierre Bruyer wrote:
> Thank you for your answer, but the function spline() (and a lot of other function in R)  can't take in its parameters the original contour which are define by a vector, i.e. :
>

If you post some reproducible code to generate the contours, someone 
will show you how to use splines to interpolate them.

Duncan Murdoch

> 	##creation of breaks for colors
> 	i<-1	
> 	paliers<- c(-1.0E300)
> 	while(i<=length(level[,1]))
> 	{
> 		paliers<- c(paliers,level[i,1])
> 		i<- i+1
> 	}
> 	paliers<- c(paliers, 1.0E300)
>
>
>
> Le 17 mai 2011 à 13:05, Duncan Murdoch a écrit :
>
> >  On 11-05-17 5:58 AM, Pierre Bruyer wrote:
> >>  I'm a French developer (so I am sorry if my english is not perfect). I have a problem to smooth the contours of a map. I have a dataset with 3 columns, x, y and z, where x and y are the coordinates of my points and z is evaluate to a qualitative elevation and his representation is a set of colors, which is define by levels.
> >>
> >>  The problem is the curve of my contour is so linear, and I would like a more continuous contour. I use the function fitted.contour to draw my map.
> >
> >  If you use a finer grid of x,y values you'll get shorter segments and they will look smoother.
> >
> >  You might be able to use a smooth interpolator (e.g. spline()) rather than linear interpolation, but those occasionally do strange things e.g.
> >
> >  x<- c(1:4, 5.9, 6:10)
> >  y<- c(1:4,   7, 6:10)
> >  plot(spline(x,y, n=200), type="l")
> >  points(x,y)
> >
> >  where one point is out of line with the others, but the curve overcompensates in order to stay smooth.
> >
> >  Duncan Murdoch
>