I need to know how to calculate the average / mean of an attribute field in my point shape file. Is this possible to do with the field calculator? I just found the options min or max but not mean. The result should be written in a new attribute field for further data processing. I would like to do this within a model.
This is a pretty late answer but you can do this in the Model Builder, a simple example is shown below:
With your vector point layer already added, you can access the Field Calculator:
In the Formula textbox, you can add your little equation to calculate the percentage. Depending on the column names of the attributes, you can use something like this:
("Altitude_Column" / Some_Total_Value) * 100
You could get statistics on that field (Vector > Analysis Tools > Basic statistics) which will tell you the mean, and then create a new attribute and use Field Calculator to fill every record with that value.