How to create different size of bubbles with different colors? [duplicate]

Question

I have a set of points with fields like 'TYPE','SIZE','SALES VOLUME',what i would like to do in QGIS is: Apply different color code by 'TYPE', Apply graduated size of bubble circles based on 'SIZE'

Havent figured out what to do with 'SALE VOLUME' yet,

but my problem is in property page, you can only define one type of style,either by TYPE or by SIZE, but how to have different size of bubble with different colors?

Answer 1

In QGIS 2.8

Double click on layer. Styles tab.

There are Marker style assigned by default, under drop down menu find Simple marker.

There will be attributes of marker, such as color and size. And small icon besides this fields which allows you to specify an expression for this attribute. (If you didn't found it, probably you haven't open dropdown list under main marker style.)

In your example, for color expression will looks like

CASE 
WHEN "TYPE"='typeA' THEN 'red' 
WHEN "TYPE"='typeB' THEN 'green'
WHEN "TYPE"='typeC' THEN 'blue'
END

Then via the same menu, you could add rules for size. Size of symbols are in millimeters so your's expression will looks like something like this

"SIZE" / 100.0

Answer 2

In QGIS 2.8 you can try the new rule based styling. There is a video about it

Answer 3

using qgis 2.8:

Right Click on your layer > go to style > add a new style and choose your style. Once you are done, add a new style and Change it. You can remove them, rename them, and copy them and do whatever you want !

Another solution if you do not have qgis <2.8 is to copy your layer

Answer 4

Qgis is not the best software for make a statistic map like proportional circle.

If you want to use Qgis, you have to build manually circle's in fonction data's.

For example, if you've value 50 and you make a circle of size 10, for value 100 you've to give a size of 20 to your circle.

If you want to make a "real" statistic map, you can use the software Philcarto.