[R-sig-Geo] Contour plot

[sownal chand]

Thanks Micha,

I would also try out your suggestion on interpolation of data.
Kind regards
Sownal

On Wed, Apr 6, 2022, 00:39 Micha Silver <tsvibar using gmail.com> wrote:

> Hi:
>
> I would point to two issues with your code. First, we should be switching
> totally to sf. You have some spatial vectors as sf classes and some as sp.
> This should be avoided today.
>
>
> Here's my version for plotting
>
>
> library(ggplot2)
> library(sf)
> library(rnaturalearth)
>
> #Draft map of Fiji
> world <- ne_countries(returnclass = "sf")
>
> Fiji <- ne_countries(country="Fiji", returnclass="sf")
> data.Fdf <- read.csv("DataR.csv")
> # Get rid of that last summary row with no coordinates!
> data.Fdf <- data.Fdf[complete.cases(data.Fdf),]
> data.sf <- st_as_sf(data.Fdf, coords=c("long", "lat"), crs="EPSG:4326")
>
> # map of Fiji Islands
> Fiji.plot <- ggplot() +
>   geom_sf(data=world) +
>   geom_sf(data=Fiji) +
>   geom_sf(data=data.sf, aes(color=Year.1965)) +
>   coord_sf(crs = 3832, # https://epsg.io/3832
>     xlim = c(2984265.06, 3539584.72), # limits are taken from projected
> bounds
>     ylim = c(-2224162.41, -1811688.88)  # of EPSG:3832
>   ) +
>   theme_bw()
>
> #Plot map of Fiji
> Fiji.plot
>
>
> But more to your question: filled.contour() is not a ggplot2 function, so
> you cannot include it in a string of ggplot elements. filled.contour()
> takes three main variables: a sequence of 'x' and 'y' values for the grid
> on which to plot the contours, and a matrix 'z' of values from which
> contours are derived. You are working with a (very) small set of *point*
> data. No matrix of values.... Typically the 'z' matrix would be created by
> interpolating between the points to get a continuous raster, then use that
> for the 'z' parameter to filled.contour().
>
>
> Given that you are covering an area of several 100 km, with only 13 data
> points (and some are almost exactly overlapping), and much of the area is
> ocean, with no measurements and probably totally different precipitation
> behavior, I don't see any clear way to get a reliable precipitation
> distribution, so no isohyetal contour lines.
> Sorry :-(
>
>
> To continue with this, I would first deal with only the main island of
> Fiji, then do a kriging interpolation of annual rainfall, year by year, and
> from those interpolated rasters, you can derive contours. You would use the
> `contour` function from `terra` package for this.
>
>
>
>
>
>
> On 05/04/2022 11:10, sownal chand wrote:
>
>
>
>
> Hello sir/madam,
>
> I have been writing codes using R and was trying to overlay contour lines
> on the map using the data set provided in the attachment. The code which I
> am working on is attached below. The problem is the overlay of the contours
> is not showing in the final map. If someone can assist in correcting the
> codes would be really appreciated .
>
>  # Packages
> #if (!require("rspatial")) remotes::install_github('rspatial/rspatial')
> library(rspatial)
> library(sp)
> library(rgdal)
> library(rgoes)
> library(raster)
> library(ggplot2)
>
> # Fiji geo data
> # download
> #Draft map of Fiji
> world <- rnaturalearth::ne_countries(scale = "Large", returnclass = "sf")
>
> # map of Fiji Islands
> Fiji <- ggplot(data=world) +
>   geom_sf() +
>   coord_sf(
>     crs = 3832, # https://epsg.io/3832
>     xlim = c(2984265.06, 3539584.72), # limits are taken from projected
> bounds
>     ylim = c(-2224162.41, -1811688.88)  # of EPSG:3832
>   )+ theme_bw()
>
> #Plot map of Fiji
> Fiji
>
> #read csv data from excel file for contoure analysis
> data.Fdf <- read.csv("C://Users/Sownal/Documents/data.csv")
> View(data.Fdf)
> class(data.Fdf)
>
> #remove NA values in the spatial Data Frame
> data.dfclean <- na.omit(data.Fdf)
> data.dfclean
>
> data.dfclean$long <- as.numeric(data$Longitude)
> data.dfclean$lat <- as.numeric(data$Latitude)
>
> # convert data to spatial data fame for spatial analysis and raster
> analysis
> data.FSP <- SpatialPointsDataFrame(data= data.dfclean, coords =
> data.dfclean$lat, data.dfclean$long)
> data.FSP
> #select one years data and overlay contours on the Map of Fiji
>
> Fiji <- ggplot(data=world) +
>   geom_sf() +
>   coord_sf(
>     crs = 3832, # https://epsg.io/3832
>     xlim = c(2984265.06, 3539584.72), # limits are taken from projected
> bounds
>     ylim = c(-2224162.41, -1811688.88)  # of EPSG:3832
>   )+ theme_bw() + filled.contour(data.dfclean$Year)
>
>
> # plot the map of Fiji with the contours lines
> Fiji
>
>
> ******************************************************************************************************
>
> Thanking you in advance
> sownalc
>
> _______________________________________________
> R-sig-Geo mailing listR-sig-Geo using r-project.orghttps://stat.ethz.ch/mailman/listinfo/r-sig-geo
>
> --
> Micha Silver
> Ben Gurion Univ.
> Sde Boker, Remote Sensing Lab
> cell: +972-523-665918
>
>

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