[R] How to produce rainfall maps

[Michael Sumner]

Fwiw the engine behind geom_raster needs explicit observation-per-row form
for input (with no structural normalization), so conversion to points is
perfectly proper here,  albeit confusing in context. (It's closer to what
graphics devices actually use ultimately, but the expansion is laid out
very early in ggplot2 because there's no standard for intermediate forms.)

Cheers, Mike

On Wed, 22 Nov 2017, 07:12 Sarah Goslee, <sarah.goslee at gmail.com> wrote:

> Hi,
>
> You might get more help from the R-sig-geo list, which is devoted to
> spatial topics.
>
> However.
>
> The *.asc file is an ArcGIS raster export format. You should use
> whatever the appropriate import commands are for your own gridded
> rainfall data. If you have a different format, you might or might not
> be able to import it directly with raster.
>
> ?raster will tell you more about the kinds of formats that function
> can handle importing.
>
> I'm not sure what the intent of converting a raster to point data
> actually is; if you have point data, then import it as point data. If
> you have gridded data, then map it as gridded data. But if it makes
> sense to you, then go for it.
>
> The comments in your code sample explain what the CSV file should be:
> coordinates of the points to be mapped.
>
> I'm not even certain from your question what your objective is.
>
> What kind of rainfall data are you starting with?
> What kind of maps do you want to produce?
>
> Sarah
>
>
>
> On Fri, Nov 17, 2017 at 3:40 AM, Stefano Sofia
> <stefano.sofia at regione.marche.it> wrote:
> > Dear R users,
> > I need to produce rainfall maps using R.
> > I know that this is possible, I looked though the web, I found the
> example below reported (the author is Andrew Tredennick).
> > I would ask you if this is the most performing way to make rainfall
> maps; if yes would someone be able to give me an example of how file.asc
> and pointfile.csv should be? If no would somebody please show me another
> way providing a small example?
> >
> > Thank you for your help
> > Stefano
> >
> >
> > library(raster)
> > library(ggplot2)
> >
> > #open ASCII file using ‘raster’ command, which converts the ASCII to a
> raster object
> > map <- raster(“/your/path/to/file.asc”)
> >
> > #convert the raster to points for plotting
> > map.p <- rasterToPoints(map)
> >
> > #Make the points a dataframe for ggplot
> > df <- data.frame(map.p)
> > #Make appropriate column headings
> > colnames(df) <- c(“Longitude”, “Latitude”, “MAP”)
> >
> > #Call in point data, in this case a fake transect (csv file with lat and
> lon coordinates)
> > sites <- data.frame(read.csv(“/your/path/to/pointfile.csv”))
> >
> > #Now make the map
> > ggplot(data=df, aes(y=Latitude, x=Longitude)) +
> > geom_raster(aes(fill=MAP)) +
> > geom_point(data=sites, aes(x=x, y=y), color=”white”, size=3, shape=4) +
> > theme_bw() +
> > coord_equal() +
> > scale_fill_gradient(“MAP (mm/yr)”, limits=c(0,2500)) +
> > theme(axis.title.x = element_text(size=16),
> > axis.title.y = element_text(size=16, angle=90),
> > axis.text.x = element_text(size=14),
> > axis.text.y = element_text(size=14),
> > panel.grid.major = element_blank(),
> > panel.grid.minor = element_blank(),
> > legend.position = “right”,
> > legend.key = element_blank()
> > )
> >
> >
> >
> >          (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.sofia at regione.marche.it
> > ---Oo---------oO----------------
> >
>
>
> --
> Sarah Goslee
> http://www.functionaldiversity.org
>
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-- 
Dr. Michael Sumner
Software and Database Engineer
Australian Antarctic Division
203 Channel Highway
Kingston Tasmania 7050 Australia

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