Hmm.
I reread in my shapeFile using readOGR() and when I summary(), I get this:
> summary(barabay)
Object of class SpatialPolygonsDataFrame
Coordinates:
min max
x -90.15208 -89.73317
y 29.18969 29.49023
Is projected: FALSE
proj4string :
[+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0]
Data attributes:
Min. 1st Qu. Median Mean 3rd Qu. Max.
1.0 1.5 2.0 2.0 2.5 3.0
My coordinates are
> summary(sightcoords)
Object of class SpatialPoints
Coordinates:
min max
coords.x1 29.19043 29.41972
coords.x2 -90.11623 -89.83532
Is projected: TRUE
proj4string :
[+proj=latlong +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0]
Number of points: 858
so it looks like my projection is close, but not identical.
When I try to spTransform() the proj4string in barabay,
spTransform(barabay, CRS("+proj=latlong +datum=WGS84 +ellps=WGS84
+towgs84=0,0,0"))
R prints out the object of barabay, including all of the lat/long values
associated with the polygons. I noticed that in the Slot "proj4string" of
the barabay that my CRS arguments match those of my sightcoords, but when I
ask for
over(sightcoords, barabay)
I get the following error message:
Error: identicalCRS(x, y) is not TRUE
A summary(barabay) gives me:
Object of class SpatialPolygonsDataFrame
Coordinates:
min max
x -90.15208 -89.73317
y 29.18969 29.49023
Is projected: FALSE
proj4string :
[+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0]
Data attributes:
Min. 1st Qu. Median Mean 3rd Qu. Max.
1.0 1.5 2.0 2.0 2.5 3.0
In the proj4string associated with barabay, what does the +no_defs mean?
Thanks for your guidance -
SR
Steven H. Ranney
On Tue, Apr 9, 2013 at 7:28 AM, Samuel Turgeon <sturgeo...@gmail.com> wrote:
> Hi Steven,
>
> You should check the projections of your datasets (summary()).
>
> When I do the same kind of analyses, I use:
>
> readOGR(), to read the shp
> proj4string(), to assign a projection
> overlay(), to make spatial overlay analysis
> spplot(), to plot more than one spatial layer
>
> hope this help
>
> Sam
>
>
> On Tue, Apr 9, 2013 at 9:10 AM, Steven Ranney <steven.ran...@gmail.com>wrote:
>
>> All -
>>
>> My apologies for what is likely a neophyte questions but I'm new to
>> spatial
>> plotting in R and to .shp files in general. I don't know all the
>> terminology which makes reading the help files that much more difficult.
>>
>> I've been asked to do a "point.in.polygon" analysis of some dolphin
>> resighting data. I have recapture coordinates for these sightings and can
>> convert them into SpatialPoints() objects. I have a .shp file (along with
>> all of the ancillary files that go with a .shp: .prj, .dbf, .sbn, .sbx,
>> .shx, .xml) with three different polygons. I read in the .shp file with
>> readShapePoly(). I can plot the .shp and the coordinates independently
>> but
>> when I ask for an over() of the coordinates and polygons, I get "NA" for
>> each of my resighting events.
>>
>> I'm sure my inability to do what I thought was a simply analyses has to do
>> with my lack of familiarity with the spatial side of R. Can anyone give
>> me
>> a hand with this? I'd like to be able to share data but unfortunately
>> it's
>> rather sensitive and will be part of a litigation.
>>
>> Thanks in advance for your assistance.
>>
>> SR
>> Steven H. Ranney
>>
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>>
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>
>
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