Skip to content

Blank certain areas of a contour plot

4 messages · Víctor Homar Santaner, Greg Snow, Duncan Murdoch

Víctor Homar Santaner
# 
Hi,

I'm interpolating a list of syncronous accumulated precipitation 
observations collected over a number of raingauge stations sited over 
land, over a regular lat/lon grid using akima's interp().

Then, I plot and locate geographycally the resulting field with a 
filled.contour() and a call to map(). Everything is fine but I need to 
"blank" (in Golden Surfer nomenclature) the areas of my domain that lay 
over the sea, as I do not have observations there and structures are 
completely artificial.

Is there any function out there that can use the mapsdata database to 
"blank" the sea areas of my plot?
Otherwise, can anybody think of a shortcut to get a similar effect on 
the final map (not showing the interpolated precipitation areas over the 
sea?

Thanks a lot in advance,

V?ctor.
1 day later
Greg Snow
# 
After you have interpolated your data, replace the values in the areas of the ocean with NA, then filled.contour will not plot in those areas.

Hope this helps,
Víctor Homar Santaner
# 
Thanks a lot for your suggestion but...
   Can  I  do that using the/a land-sea information from the 'worldHires'
   database (from mapdata)?
   Best,
   V??ctor.
Greg Snow wrote:
After you have interpolated your data, replace the values in the areas of the o
cean with NA, then filled.contour will not plot in those areas.

Hope this helps,

  

-----Original Message-----
From: [1]r-help-bounces at r-project.org [[2]mailto:r-help-bounces at r-
project.org] On Behalf Of Victor Homar
Sent: Tuesday, September 16, 2008 9:54 AM
To: [3]r-help at r-project.org
Subject: [R] Blank certain areas of a contour plot

Hi,

I'm interpolating a list of syncronous accumulated precipitation
observations collected over a number of raingauge stations sited over
land, over a regular lat/lon grid using akima's interp().

Then, I plot and locate geographycally the resulting field with a
filled.contour() and a call to map(). Everything is fine but I need to
"blank" (in Golden Surfer nomenclature) the areas of my domain that lay
over the sea, as I do not have observations there and structures are
completely artificial.

Is there any function out there that can use the mapsdata database to
"blank" the sea areas of my plot?
Otherwise, can anybody think of a shortcut to get a similar effect on
the final map (not showing the interpolated precipitation areas over
the
sea?

Thanks a lot in advance,

V??ctor.

--
-----------------------------------------------------------------------
V??ctor Homar Santaner
Grup de Meteorologia

Edif. Mateu Orfila                      Tel: +34 971 17 1376
Universitat de les Illes Balears        Fax: +34 971 17 3426
07122 Palma de Mallorca (SPAIN)         Email: [4]Victor.Homar at uib.es

              Knowledge is contagious. Infect truth.

______________________________________________
[5]R-help at r-project.org mailing list
[6]https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide [7]http://www.R-project.org/posting-
guide.html
and provide commented, minimal, self-contained, reproducible code.





--
-----------------------------------------------------------------------
V??ctor Homar Santaner
Grup de Meteorologia

Edif. Mateu Orfila                      Tel: +34 971 17 1376
Universitat de les Illes Balears        Fax: +34 971 17 3426
07122 Palma de Mallorca (SPAIN)         Email: [8]Victor.Homar at uib.es

              Knowledge is contagious. Infect truth.
-----------------------------------------------------------------------

References

   1. mailto:r-help-bounces at r-project.org
   2. mailto:r-help-bounces at r
   3. mailto:r-help at r-project.org
   4. mailto:Victor.Homar at uib.es
   5. mailto:R-help at r-project.org
   6. https://stat.ethz.ch/mailman/listinfo/r-help
   7. http://www.R-project.org/posting
   8. mailto:Victor.Homar at uib.es
Duncan Murdoch
#
On 9/17/2008 2:29 PM, Victor Homar wrote:
Yes, you use the map.where function to identify the location of the 
points.  If NA, it's out in the ocean somewhere.  Some lakes and 
interior seas will probably be identified by name.  For example, here's 
what I get when clicking on some regions in the world map:

 > map("world")
 > loc <- locator()
 > loc
$x
[1]  -47.35604 -150.58010 -114.14808  -86.82406

$y
[1] 33.67133 42.77815 62.20602 44.59951

 > map.where(x=loc$x, y=loc$y)
[1] NA
[2] NA
[3] "Canada"
[4] "Great Lakes:Superior, Huron, Michigan"

I believe all of those locations were in the oceans (1 and 2) or lakes 
(3 and 4).

Duncan Murdoch