# NetCDF files (*.nc) can be read by a variety of softwares
# (e.g., C, C++, Fortran, Phyton, R, Matlab)
# For more information on NetCDF files please visit:
#    http://www.unidata.ucar.edu/software/netcdf/

# This is a generic R program to read arrays from the
# Very High Resolution Climatology NetCDF files:
#     VHRFC.nc - Very High Resolution Full Climatology
#     VHRAC.nc - Very High Resolution Annual Cycle
#     VHRDC.nc - Very High Resolution Diurnal Cycle
#     VHRMC.nc - Very High Resolution Monthly Cycle
#     VHRSC.nc - Very High Resolution Seasonal Cycle
#
# Written by: Rachel Albrecht, University of Sao Paulo, Brazil

#---------------------------------------------------------------
# R is a free software environment for statistical computing
# and graphics. It compiles and runs on a wide variety of UNIX
# platforms, Windows and MacOS.
# To download R, please choose your preferred CRAN mirror:
#    https://cran.r-project.org/mirrors.html
# More information can be found at R Project homepage:
#    https://www.r-project.org/
#----------------------------------------------------------------

# This program requires "ncdf4" package
# (https://cran.r-project.org/web/packages/ncdf4/index.html)
# For a simple installation, use the command below:
#    install.packages("ncdf4")

require(ncdf4)

#-- Opening an existing netCDF file for reading
ncin <- nc_open("VHRFC.nc")
    #-- Printing on screen NetCDF variables, dimensions and attributes
    print(ncin)
    #-- Reading SDS arrays and grids from an existing netCDF file:
    #   Available SDS names are:
    #       Longitude
    #       Latitude
    #       VHR*C_LIS_FRD (=Flash Rate Density)
    lon <- ncvar_get(ncin,"Longitude") 
    lat <- ncvar_get(ncin,"Latitude",verbose=F)
    head(lat)
    frd <- ncvar_get(ncin,"VHRFC_LIS_FRD",verbose=F)
    #-- Reading Global attributes
    att<-ncatt_get( ncin,0)
    #-- Reading FRD attritubutes
    attfrd <- ncatt_get( ncin,"VHRFC_LIS_FRD")
#-- Closing an open netCDF file
nc_close(ncin)

#-- printing on screen the first or last parts of the variable
head(lon)
head(lat)
head(frd)

# To read other data sets (e.g., VHRAC.nc, VHRDC.nc, VHRMC.nc, VHRSC.nc) just replace the file name
# and varid in nc_open() and ncvar_get() functions above.