AdehabitatHR R package issue with Writing Shape Files

[Kyle Shaney]

Hi All,

I am trying to export a shapefile of a minimum convex polygon, but I receive the following error message:

Error: is(x, "SpatialPolygonsDataFrame") is not TRUE

I was able to successfully get my minimum convex polygon and plot it in R using the following code: 

PID208 <- read.csv(file="PID208.csv", header = TRUE, sep = ",")

head(PID208)

    Name      X       Y        X1       Y2 sex age        Receive.Time

1 PID208 391734 6744220 -148.9906 60.81855   2   3 2015.06.18 21:12:20

2 PID208 391738 6744219 -148.9905 60.81855   2   3 2015.06.18 22:50:30

3 PID208 391739 6744229 -148.9905 60.81864   2   3 2015.06.04 20:41:52

4 PID208 391748 6744229 -148.9904 60.81864   2   3 2015.06.04 20:44:27

5 PID208 391748 6744229 -148.9904 60.81864   2   3 2015.06.04 20:44:27

6 PID208 391743 6744229 -148.9904 60.81864   2   3 2015.06.04 22:07:07​

xy<- SpatialPoints(PID208 [2:3]) 
mcp(xy, percent=95)
mcp(xy, percent=95)$area 
plot(mcp(xy,percent=100))

Anybody know what I might be missing to successfully export the file for use in GIS?

Thanks!

Kyle

Thanks!

Kyle

[Kyle Shaney]

Sorry, I used the following command at the end to try and export the shape file:

writePointsShape(mcp,"208mcp.shp")

[Nick van Doormaal]

Hi Kyle,

I think you have to save the mcp as an object first before exporting it. Also make sure to load the rgdal-package (in case you haven't)

library(rgdal)

xy<- SpatialPoints(PID208 [2:3]) 

xy.mcp <-  mcp(xy, percent=95)

writeOGR(xy.mcp, dsn = '.', layer = 'xy.mcp', driver = "ESRI Shapefile")

This will save the shapefile in the current working directory. Does this work for you?

Cheers,

Nick

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[Nick van Doormaal]

try writePolyShape(mcp, "208mcp.shp")

Cheers,

Nick

--

[Jeffrey Evans]

The issue is that "xy" is a SpatialPoints object and not SpatialPointsDataFrame, meaning that there are no associated attributes. An easy fix is to just coerce it to the correct object with a dummy attribute (eg., sequential ID's).

 xy <- SpatialPointsDataFrame(xy, data.frame(ID=1:length(xy))

The "xy" object is now a SpatialPointsDataFrame and you can use rgdal::writeOGR to write to a shapefile. Using rgdal retains projection information so, is preferable to using maptools. 

Best,
Jeff

Jeffrey S. Evans, PhD., | Senior Landscape Ecologist 

The Nature Conservancy | Global Lands Science Team

Affiliate Assistant Professor | Zoology & Physiology | University of Wyoming

Laramie, WY | jeffre...@tnc.org | (970) 672-6766