Again, coordinate interpolation with NAs

I need a new set of coordinates interpolated at a given resolution,
let's say one data point each xx kilometers or degrees, or at a given
proportion of the total length, etc.

Think of this coordinates as transect points, and I need to keep the
NAs, since they mark cut offs in my transect.

Mario A. Pardo skreiv:

I need a new set of coordinates interpolated at a given resolution,
let's say one data point each xx kilometers or degrees, or at a given
proportion of the total length, etc.

Think of this coordinates as transect points, and I need to keep the
NAs, since they mark cut offs in my transect.

I would recommend using SpatialLines objects instead, which can 
easily hold polylines and multiple lines. Example:

library(sp)
library(geosphere)

lon=c(-115.86, -115.83, NA, -115.78, -115.78, -115.75, NA, -115.68, -115.66)
lat=c(  29.76,   29.61, NA,   29.55,   29.53,   29.41, NA, 29.13, 29.09)
d=data.frame(lon,lat)        # Convert to data frame
d$group=cumsum(is.na(d$lon)) # Add line ID
d=d[!is.na(d$lon),]          # Remove NA rows

d.lines=split(d,d$group)    # Split by line ID

# Convert into SpatialLines object
d.sp=SpatialLines(lapply(d.lines, function(df) Lines(Line(df[c("lon","lat")]), ID=df$group[1])),
                  proj4string=CRS("+proj=longlat"))

# Add intermediate points
d.sp.int=makeLine(d.sp, interval=1000)


# The actual coordinates are available in this list
# (though I don?t know why there are duplicates ?
# a small bug in makeLine, perhaps?):
lapply(d.sp.int at lines, function(x) x at Lines[[1]]@coords)

Hi all,

I'm changing the way of my question, since it was missunderstood before.

Given:

lon <- c(-115.86, -115.83, NA, -115.78, -115.78, -115.75, NA, -115.68, 
-115.66)
lat <- c(  29.76,   29.61, NA,   29.55,   29.53,   29.41, NA, 29.13,   29.09)

I need a new set of coordinates interpolated at a given resolution, let's say 
one data point each xx kilometers or degrees, or at a given proportion of the 
total length, etc.

BUT,

Think of this coordinates as transect points, and I need to keep the NAs, 
since they mark cut offs in my transect. The only think that I need is to 
increase the number of data points in each transect. That means that the 
new.lon would be constitued by values interpolated between the first two 
points (-115.86 and -115.83); after them, a NA should be placed, marking a 
cut off in the transect, then the interpolated data of the next three points 
(-115.78, -115.78 and -115.75), then a NA... and so forth. Off course, the 
new.lat should be the same length as new.lon with NAs placed at the same 
places. As far as I have tried, neither the function "approx" or 
"expand.grid" can do that. I know this is not a Matllab list, but since I 
recently moved from Matlab to R, I just want to point out that the function 
"interpm" does exactly that, just in case somebody here knows it.

Thanks! and sorry for the insistence.