[R-sig-Geo] How do I read and plot .nc data in R?

[Eko Susilo]

Hi Micheal,

I have tried do your scripts,
/y <- raster(fname, xmn=-20, xmx=25, ymn=90, ymx=144)//
//projection(y) <- CRS("+proj=longlat +datum=WGS84")/
the result is good, but not georeference image (i mean the data is not 
right position), you can see my plot here 
https://onedrive.live.com/redir?resid=6FFDD661570C7D0A%21163

Meanwhile  when I read .nc directly and plot the data is look like 
https://onedrive.live.com/redir?resid=6FFDD661570C7D0A%21164 
<https://onedrive.live.com/redir?resid=6FFDD661570C7D0A%21163>
not georeferenced image  but in the right position)

The .nc data available in this link 
https://onedrive.live.com/redir?resid=6FFDD661570C7D0A%21165


On 19/12/2014 17:04, Michael Sumner wrote:
>
> If you could easily convert it to raster, raster is the best place to 
> start.
> Try
>
> library(raster)
> r = raster(fname)
> plot(r)
>
> Please report on the effect.
>
> Netcdf is *so* general a format it really can come down to specifics. 
> If you can it is best to share a link to the or a representative file.
>
> Cheers, Mike
>
>
> On Fri, 19 Dec 2014 19:05 Eko Susilo <ekosusilo at live.com 
> <mailto:ekosusilo at live.com>> wrote:
>
>     Could somebody help me to figure out my data
>
>     I have .nc data around Indonesia water (attached below)
>
>     I use R to open and plot it. This is my syntax
>
>     nc <- open.ncdf(choose.files('D:/R/yfin_pelikan/yfin_input', caption =
>     'Select netcdf Files .....'))
>     print (nc)
>
>     # Read the variable
>
>     adl <- nc$var[[1]]
>     varsize <- adl$varsize
>     ndims <- adl$ndims
>     nt <- varsize[ndims]
>
>     start <- rep(1,ndims) # begin with start=(1,1,1,...,1)
>     start[ndims] <- j # change to start=(1,1,1,...,i) to read timestep i
>     count <- varsize # begin w/count=(nx,ny,nz,...,nt), reads entire var
>     count[ndims] <- 1 # change to count=(nx,ny,nz,...,1) to read 1 tstep
>
>     data <- get.var.ncdf(nc, adl, start=start, count=count )
>
>     # plot the map
>
>     jet.colors <- colorRampPalette(c('#00007F', 'blue', '#007FFF',
>     'cyan','#7FFF7F', 'yellow', '#FF7F00', 'red', '#7F0000'))
>
>     plot.adl <- levelplot(data,
>     col.regions = jet.colors(255), at=seq(0, 1, 0.005),
>     yscale.components=yscale.raster.subticks,
>     xscale.components=xscale.raster.subticks,
>     margin=FALSE, ylab='latitude', xlab='longitude', main='test')
>     print(plot.adl + layer(sp.lines(indo.map, lwd=1, col='black')))
>
>     # The results is good bad not georreference so i can't overlay
>     with the
>     base map (costaline)...
>
>     # So i try to convert it to raster
>
>     # Convert it to raster and re-plot
>
>     y <- raster(data.adl, xmn=-20, xmx=25, ymn=90, ymx=144)
>     projection(y) <- CRS("+proj=longlat +datum=WGS84")
>
>     plot.y <- levelplot(y,
>     col.regions = jet.colors(255), at=seq(0, 1, 0.005),
>     yscale.components=yscale.raster.subticks,
>     xscale.components=xscale.raster.subticks,
>     margin=FALSE, ylab='latitude', xlab='longitude', main='test')
>     print(plot.y + layer(sp.lines(indo.map, lwd=1, col='black')))
>
>     # The result is not good..
>
>     Attached file:
>
>     data (https://onedrive.live.com/redir?resid=6FFDD661570C7D0A%21165
>     <https://www.researchgate.net/go.Deref.html?url=https%3A%2F%2Fonedrive.live.com%2Fredir%3Fresid%3D6FFDD661570C7D0A%2521165>)
>
>     result1 (https://onedrive.live.com/redir?resid=6FFDD661570C7D0A%21164
>     <https://www.researchgate.net/go.Deref.html?url=https%3A%2F%2Fonedrive.live.com%2Fredir%3Fresid%3D6FFDD661570C7D0A%2521164>)
>
>     result2 (https://onedrive.live.com/redir?resid=6FFDD661570C7D0A%21163
>     <https://www.researchgate.net/go.Deref.html?url=https%3A%2F%2Fonedrive.live.com%2Fredir%3Fresid%3D6FFDD661570C7D0A%2521163>)
>
>
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>
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