overlapping-featurespolygonqgisvector
I am working in QGIS on a vector layer where areas are classified using an attribute "typo". The problem I'm encountering is that many polygons are duplicated or overlapping, with the result that some areas are classified as two or more "typo". This is an error.
In order to make some statistical analysis I need to clean this layer removing the overlapping/duplicates so that every inch of territory is classified as one and only one "typo"; which one is indifferent. How can I perform it?
These are a few tools I use to cleanup lines:
What I'd like to do is basically create a dummy variable called CBSA with a 1 for CBSA counties (red in the map) and a 0 for those not.
I'm no spatial expert, but maybe you tweak something based on this:
library(rgeos)
# shrink the cbsa polygons a bit to play it safe:
cbsa_b <- gBuffer(cbsa, byid=TRUE, width=-0.05)
# get intersection matrix:
m <- gIntersects(county, cbsa_b, byid=TRUE)
# which county polygons intersect any cbsa?
in_cbsa <- colSums(m)>0
in_cbsa is the dummy variable CBSA with TRUE (or 1 if you make it in_cbsa+0L) for CBSA counties:
head(in_cbsa)
# 0 1 2 3 4 5
# FALSE FALSE FALSE TRUE TRUE TRUE
sum(in_cbsa)
# [1] 1868
# plot to verify:
library(ggplot2)
county_f <- fortify(county)
cbsa_f <- fortify(cbsa)
ggplot() +
geom_polygon(aes(long,lat,group=group), county_f, fill=NA, color="black") +
coord_quickmap(xlim=c(-128,-75), ylim=c(25,55)) +
geom_polygon(aes(long,lat,group=group), cbsa_f, fill="red", color=NA) +
geom_polygon(aes(long,lat,group=group), county_f[county_f$id %in% names(which(!in_cbsa)), ], fill="blue", color=NA, alpha = .3)
Best Answer
To remove duplicates:
You can use the Delete duplicate geometries tool by accessing it via the Processing Toolbox:
Another option is to use the v.clean tool from GRASS and select the rmdupl option:
To remove overlaps:
You can use the Dissolve tool, provided there are common attributes between the original polygon and the overlapping polygon:
As always, you can manually remove them if there are only a handful. You can do this via the Attribute Table, find your overlapping polygons (useful in conjunction with a topology checker to highlight the overlaps) and select the option to delete features.