Re: [R-sig-Geo] help: Problem getting centroids inside lists
If all of your data frames had enough points then this should work:
myfun1 <- function(le) {
list(one=geosphere::centroid(coordinates(le$one)),
two=geosphere::centroid(coordinates(le$two))
)
}
lapply(ct, myfun1)
To handle the one point case, try the following, which I think works with your
example data, but is untested if there just two points.
It also assumes the data frames are named 'one' and 'two', and will ignore any
others. To handle other names, I think you
could replace $one with [[1]] and $two with [[2]] .
myfun <- function(le) {
list(one=if (length(le$one)>1) geosphere::centroid(coordinates(le$one)) else
coodinates(le$one),
two=if (length(le$two)>1) geosphere::centroid(coordinates(le$two)) else
coordinates(le$two)
)
}
lapply(ct, myfun)
To see a little bit of what's going on, try
myfun(ct[[1]])
myfun1(ct[[1]])
myfun1(ct[[2]])
myfun(ct[[2]])
I would also verify that the length method for objects of class SpatialPoints
does return the number of points, as it appears to:
> class(ct$a$two)
[1] "SpatialPoints"
attr(,"package")
[1] "sp"
> length(ct$a$one)
[1] 3
> length(ct$a$two)
[1] 3
> length(ct$a$two)
[1] 3
> length(ct$b$two)
[1] 1
--
Don MacQueen
Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062
Lab cell 925-724-7509
On 9/10/18, 10:56 AM, "R-sig-Geo on behalf of Ariel Fuentesdi"
wrote:
Hi everyone,
I have a list of coordinates called "ct" and I want to extract the
centroids of each sublist, but it only works when it has only 3 or more
points. In ct$b$two only has one point; in that case, I would rescue that
point as If it were a centroid.
This is what I did:
library(dplyr)
library(geosphere)
ct <- list(a = list(one = data.frame(lon = c(-180, -160, -60), lat = c(-20,
5, 0)),
two = data.frame(lon = c(-18, -16, -6), lat = c(-2, 50,
10))),
b = list(one = data.frame(lon = c(-9, -8, -3), lat = c(-1, 25,
5)),
two = data.frame(lon = c(-90), lat = c(-1
coordinates(ct$a$one) <- ~lon+lat
coordinates(ct$a$two) <- ~lon+lat
coordinates(ct$b$one) <- ~lon+lat
coordinates(ct$b$two) <- ~lon+lat
s <- 1:length(ct)
ctply <- list()
for (i in s){
for (j in 1:length(ct[[i]])) {
ctply[[i]][j] <- ifelse(test = lengths(ct[[i]][1]) > 2, yes = sapply(X =
ct[[i]][j],
FUN = function(y) geosphere::centroid(slot(y, "coords"))), no =
ct[[i]][j] )
}
}
Thanks in advance
Regards,
Ariel
[[alternative HTML version deleted]]
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[R-sig-Geo] Isohyet maps where the inverse distance method does not work correctly
Dear list users,
I implemented a code for creation of snowfall isohyets through the inverse
distance method applied to a Digital Elevation Model.
Within a big area (approximatively 2.000 km2) I use only six stations, I would
expect the snowfall esteem getting smaller with higher distances from the
stations.
In my case the snowfall values remain constant all over the area.
This is the relevant part of my code (df_prec is the data frame that contains
the coordinates of the stations and the snowfall cumulates).
Could somebody be so patient to spot where is my (big) mistake? (Here attached
- as exception - the file picture1.pdf is an example of the result.)
Thank you for your attention and your help
Stefano Sofia
## LOADING SHAPEFILE FOR AREA5
Shape_area <- readOGR(dsn="area.shp", layer="area")
Shape_area_projection <- "+init=epsg:32633 +proj=utm +zone=33 +datum=WGS84
+units=m +no_defs +ellps=WGS84 +towgs84=0,0,0"
Shape_area <- spTransform(Shape_area, CRS(Shape_area_projection))
## LOADING DEM
area_DEM raster("dem.tif")
area_DEM <- projectRaster(area_DEM, crs = CRS("+init=epsg:32633"))
## EXTRACTING THE ELEVATION VALUES TO MY POINTS
df_prec$ExtractedElevationValues <- extract(x=area_DEM, y=df_prec)
## CREATING A NEW GRID
newgrid <- as(area_DEM, "SpatialGridDataFrame")
newgrid <- raster(newgrid)
names(newgrid) <- "ExtractedElevationValues"
## Inverse Distance Weighted
if (sum(df_prec$Cumulata) > 0)
{
OK_rain <- gstat(formula=snowfall_cumulate~ExtractedElevationValues,
data=df_prec, locations=newgrid)
rain_rast <- interpolate(newgrid, OK_rain, xyOnly=FALSE, na.rm=FALSE)
} else
{
rain_rast <- raster(df_prec)*0
}
(oo)
--oOO--( )--OOo
Stefano Sofia PhD
Area Meteorologica e Area nivologica - Centro Funzionale
Servizio Protezione Civile - Regione Marche
Via del Colle Ameno 5
60126 Torrette di Ancona, Ancona
Uff: 071 806 7743
E-mail: stefano.so...@regione.marche.it
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picture1.pdf
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