[Qgis-user] Re: how to group a classified unique symbology in the layer properties box

[Ramon Andinach]

On 21/04/2011, at 01:52 , pevins wrote:

> Thanks for the suggestion, but The values I want to group are not integers,
> they are text. Symbols I want to group do not necessary sort after each
> other (I.e. Granite comes after gabbro, but i would certainly not want to
> group them together in a graduated interval). I need to be able to manually
> select the symbols I want to group.

Funny, I'd just mentally gone, so like in the geology file, where there's granite, and feldspar granite and Robert's granite and then you say it just there.

I see two sensible ways to this.

1. The biggest and ugliest geology shape I have, and that I've only partly recoloured [1], as a unit name and a rock-type column. The unit name is granite, feldspar granite, Robert's granite, etc., but in the rock-type they're listed as granite. So naturally I'm using the rock-type column. You could make or use a column like that.

2. You could also get a similar effect using a rule-based symbology definition. Unit-name = 'granite' AND unit-name = 'feldspar-granite' etc.

Those are the two neatest.


There is a third that I'm using, but it's not pretty or nice. It is very, very ugly.
For one of my purposes the maps cover a small area (usually <10km wide), and I only need very, very coarse detail. This shape file doesn't have a rock-type as such, but I've made a unique symbology where I've been through and changed the colours so that all of the basalt-like rocks have the same shade of green [2]. This is really ugly when I make a legend on a new print composer, because there's hundreds liths in the column. Then I change the first basalt-like unit in the legend to "basalts" or "basaltoids" or similar, and weed out the rest of the basalt like rocks, repeat for granites and whatever other rocks are on your screen. This is where QGIS is helpful, because next time I open this composer, it remembers my weeding. 
It's a really ugly kludge, but for the purpose will do.


I'd use one of the first two :)


-ramon.
[1.] The original cartography is in a proprietary binary format. I'm sure this has happened to most of us before.
[2.] I also have a saved symbology for this where they have slightly different colours for when I need more detail.