Ale,
Some remarks between the lines:
Alessandro schreef:
Thanks for All help give me.
I spoke with my professor and now I must do some changes. After
subtract the column Z with clomun DEM_SGRD to obtain column H. I wish
to create a new shape with only this H column. I tried and tried but
when I write the shape file there is always an error.
Sorry for all disturb.
I don’t want to be ill-mannered, to use improperly your time, but
before to save the shape is It possible to save only all records with
H value > of 2. (the statistical analysis need this clean)
Thanks
Ale
> prova <- readOGR(".", "prova")
OGR data source with driver: ESRI Shapefile
Source: ".", layer: "prova"
with 42 rows and 2 columns
> summary(prova)
Object of class SpatialPointsDataFrame
Coordinates:
min max
coords.x1 267980.1 267998.1
coords.x2 4147799.4 4147818.8
Is projected: NA
proj4string : [NA]
Number of points: 42
Data attributes:
Z DEM_SGRD
Min. :1415 Min. :1412
1st Qu.:1419 1st Qu.:1413
Median :1421 Median :1414
Mean :1423 Mean :1414
3rd Qu.:1424 3rd Qu.:1415
Max. :1437 Max. :1417
> prova$H <- prova$Z - prova$DEM_SGRD
> summary(prova)
Object of class SpatialPointsDataFrame
Coordinates:
min max
coords.x1 267980.1 267998.1
coords.x2 4147799.4 4147818.8
Is projected: NA
proj4string : [NA]
Number of points: 42
Data attributes:
Z DEM_SGRD H
Min. :1415 Min. :1412 Min. : 3.169
1st Qu.:1419 1st Qu.:1413 1st Qu.: 5.612
Median :1421 Median :1414 Median : 7.320
Mean :1423 Mean :1414 Mean : 9.265
3rd Qu.:1424 3rd Qu.:1415 3rd Qu.:10.982
Max. :1437 Max. :1417 Max. :21.806
> prova2 <- prova$H
Here you extract the data from prova, not including the coordinates.
Look at class(prova2) to see that it is no longer a
SpatialPointsDataFrame but a data.frame. Use the following syntax to get
the data plus the coordinates:
prova2 <- prova["H"]
Now you can export it using write OGR. To get only the values above H == 2:
prova_Hgt2 = prova2[prova2$H > 2,]
Or combining the two actions above into one command:
prova2 = prova[prova$H > 2, "H"]
cheers,
Paul
> summary(prova2)
Min. 1st Qu. Median Mean 3rd Qu. Max.
3.169 5.612 7.320 9.265 10.980 21.810
> writeOGR(prova2, ".", "prova2", driver="ESRI Shapefile")
Errore in writeOGR(prova2, ".", "prova2", driver = "ESRI Shapefile") :
obj of wrong class
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Drs. Paul Hiemstra
Department of Physical Geography
Faculty of Geosciences
University of Utrecht
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http://intamap.geo.uu.nl/~paul
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