I've a vector map of areas created from the raster original using
r.to.vect with the '-v' option. The vector map's attribute table has cat
values which is sufficient for me to identify specific polygons. However,
when displaying the map the lables do not appear despite the attr and cat
options being selected.
What procedure will allow me to identify why the labels don't display so I
can fix the problem?
Rich
Hi Rich,
I’ve had this problem before and for me it always seemed to be an issue of setting the size of labels correctly, which can be tricky sometimes, particularly if your location is latlong (if I remember correctly the size is in map units, so in that case you need to compute your desired label size as degrees).
It’s been a while since I’ve had to do this though, so I’m not 100% certain of this, but perhaps it will solve your problem.
Best,
Nick
On Mon, May 28, 2012 at 4:43 AM, Rich Shepard <rshepard@appl-ecosys.com> wrote:
I’ve a vector map of areas created from the raster original using
r.to.vect with the ‘-v’ option. The vector map’s attribute table has cat
values which is sufficient for me to identify specific polygons. However,
when displaying the map the lables do not appear despite the attr and cat
options being selected.What procedure will allow me to identify why the labels don’t display so I
can fix the problem?Rich
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On Mon, 28 May 2012, Nick Jachowski wrote:
I've had this problem before and for me it always seemed to be an issue of
setting the size of labels correctly, which can be tricky sometimes,
particularly if your location is latlong (if I remember correctly the size
is in map units, so in that case you need to compute your desired label
size as degrees).It's been a while since I've had to do this though, so I'm not 100% certain
of this, but perhaps it will solve your problem.
Nick,
It is a reasonable suggestion, but not the solution here. I raised the
label size from the default 8 pixels to 20 pixels, then 40 pixels, but there
was still no display.
I'm still open to suggestions, recommendations, and solutions.
Thanks,
Rich
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Applied Ecosystem Services, Inc. | Helping Ensure Our Clients' Futures
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On 27/05/12 23:43, Rich Shepard wrote:
I've a vector map of areas created from the raster original using
r.to.vect with the '-v' option. The vector map's attribute table has cat
values which is sufficient for me to identify specific polygons. However,
when displaying the map the lables do not appear despite the attr and cat
options being selected.
You have to display the centroids to be able to see labels, i.e.
d.vect census_wake2000 display=shape,cat type=point,line,boundary,area,face
will not display the cat values, while
d.vect census_wake2000 display=shape,cat type=point,line,boundary,area,face,centroid
will.
No need to use attr if all you want to see are the categories of the features (unless your attribute table's cat column does not correspond to the category values of the features, but represents a separate attribute, then attr is needed, but cat not.)
Moritz
On Tue, 29 May 2012, Moritz Lennert wrote:
You have to display the centroids to be able to see labels, i.e.
Moritz,
You lead me to the solution. There is one default choice that must be
maintained (the centroid checkbox on the Selections tab) and one non-default
that needs to be selected: the the 'Display category number of features' on
the Required tab. I had consistently left the centroids selected for
display, but on the Required tab had checked the 'Display selected attribute
from attrcol' box rather than the 'Display category number of features' box.
Because the category numbers column appears on the Labels tab as a choice
for display I interpreted it as an attribute column and missed the
second-from-the-top choice on the Required tab.
Thank you very much,
Rich
On 29/05/12 14:58, Rich Shepard wrote:
On Tue, 29 May 2012, Moritz Lennert wrote:
You have to display the centroids to be able to see labels, i.e.
Moritz,
You lead me to the solution. There is one default choice that must be
maintained (the centroid checkbox on the Selections tab) and one
non-default
that needs to be selected: the the 'Display category number of features' on
the Required tab. I had consistently left the centroids selected for
display, but on the Required tab had checked the 'Display selected
attribute
from attrcol' box rather than the 'Display category number of features'
box.Because the category numbers column appears on the Labels tab as a choice
for display I interpreted it as an attribute column and missed the
second-from-the-top choice on the Required tab.
Well, actually, it should work both ways, i.e. with the
d.vect census_wake2000 display=shape,attr type=point,line,boundary,area,face,centroid attrcol=cat
d.vect census_wake2000 display=shape,cat type=point,line,boundary,area,face,centroid
should give the same result (assuming that all features that have a category value have a corresponding entry in the cat column of the attribute table).
Note that in grass7.0 the use of centroids is not necessary anymore.
Moritz