Hello there,
I am trying to overlay a global map with ncdf data of precipitation for a
particular location (using specific coordinates). The file is in ncdf format
(commonly used to store away climate data), and I am currently attempting to
place a global map on plotted precipitation values. However, I am having
difficulty placing a global map on this plot and am encountering errors. I
will show you what I have done:
#To create a plot of precipitation data using the following ncdf file - the
following works fine and provides the distributions global precipitation
values (Land+Water values):
library(ncdf4)
Can<-"MaxPrecCCCMACanESM2rcp45.nc"
>Model<-nc_open(Can)
>print(Model)
>attributes(Model$var)
>$names
>dat<-ncvar_get(Model, "onedaymax")
>dat[128,50,1] #View onedaymax for selected latitude, longitude and Year
>nc_lat<-ncvar_get(Model,attributes(Model$dim)$names[2]) #Retrieve latitude
>nc_lon<-ncvar_get(Model,attributes(Model$dim)$names[3]) #Retrieve longitude
>print(paste(dim(nc_lat), "latitudes and", dim(nc_lon), "longitudes"))
>library(maptools)
>map<-dat[,,5] #Precipitation for all longitudes, latitudes, and Year 5
>grid<-expand.grid(nc_lon=nc_lon, nc_lat=nc_lat)
>image(nc_lon,nc_lat,map, ylab="Latitude", xlab="Longitude", main="One-day
maximum precipitation")
>levelplot(map~nc_lon*nc_lat, data=grid, at=cutpoints, cuts=11,
ylab="Latitude", xlab="Longitude", >main="Year 5 one-day maximum
precipitation (mm/day) for CanESM2 under RCP4.5", pretty=T,
col.regions=(rev(brewer.pal(10, "Spectral"))))
#To place a global map on the map that map that returns using the above
code. *This is where errors begin:
>ggplot()+geom_point(aes(x=nc_lon,y=nc_lat,color="onedaymax"),
size=0.8)+borders("world",
colour="black")+scale_color_viridis(name="onedaymax")+theme_void()+coord_quickmap()
*Error: Aesthetics must be either length 1 or the same as the data (128): x,
y, colour*
Why doesn't this work? Could it be that I am not including the "time"
dimension in the ggplot function? The problem, though, is when I try to
obtain the "time" dimension, like I did for latitude and longitude, I
receive the following error:
t<-ncvar_get(Model,"time")
*Error in nc$dim[[idobj$list_index]] :
attempt to select more than one element*
If it helps, this is what the variables and dimensions look like in the ncdf
file:
/File MaxPrecCCCMACanESM2rcp45.nc (NC_FORMAT_NETCDF4):
3 variables (excluding dimension variables):
double onedaymax[lon,lat,time] (Contiguous storage)
units: mm/day
double fivedaymax[lon,lat,time] (Contiguous storage)
units: mm/day
short Year[time] (Contiguous storage)
3 dimensions:
time Size:95
lat Size:64
units: degree North
lon Size:128
units: degree East/
Any help would be greatly appreciated!!!!
Thanks,
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