Intersect shapefiles

Such a clear and simple explanation - thank you.  I wish the function
documentation was written like that.

-----Original Message-----
From: Alex Mandel [mailto:tech_dev at wildintellect.com]
Sent: Thursday, February 18, 2016 9:59 AM
To: Worrall, James -FS <jworrall at fs.fed.us>; chris english <
englishchristophera at gmail.com>; A. Marcia BARBOSA <barbosa at uevora.pt>
Cc: Help R-Sig_Geo <r-sig-geo at r-project.org>
Subject: Re: [R-sig-Geo] Intersect shapefiles

Union creates a merged shape including all parts of input objects.

Intersection creates a shape of the overlapping portions of input objects.

I'm not clear on the goal from the initial email so I don't know which is
better in this case.

Enjoy,
Alex

On 02/18/2016 07:55 AM, Worrall, James -FS wrote:

I would have thought gUnaryUnion, but then I can't understand from the

documentation what the difference is between that and gIntersection.

-----Original Message-----
From: R-sig-Geo [mailto:r-sig-geo-bounces at r-project.org] On Behalf Of
chris english
Sent: Thursday, February 18, 2016 7:24 AM

John,

As Loic suggests, rgeos::gIntersection will get you there. Look closely

at his naming of objects and your example code using spTransform. With his
approach, each object has its own name; whereas your approach overwrites
Rain_poly_merge the second and third time and the final object (third) is
the 2008 maize yield. So read your shapefiles into differently named
objects and use Loic's approach.

Chris





This electronic message contains information generated by the USDA

solely for the intended recipients. Any unauthorized interception of this
message or the use or disclosure of the information it contains may violate
the law and subject the violator to civil or criminal penalties. If you
believe you have received this message in error, please notify the sender
and delete the email immediately.