7.6.7. Basic statistics, list unique values

 Especially for large vector data files containing a variety of attribute fields and features, it can be useful to display some statistical information before performing calculations with these attribute values. Two very useful tools are provided by the fTools plugin (see section 7.1.3.) and explained in the following examples:

To display basic statistics based on attributes,

  1. Go to Vector.
  2. Select Analysis Tools.
  3. Choose Basic statistics.
  4. Any vector layer can be chosen within the QGIS project as Input Vector Layer.
  5. Select a target field, where the statistics (mean value, standard deviation, sum, minimum, maximum etc.) should be performed.
  6. Click OK (Fig. 101).

Sometimes the total number of attribute values within a given field are not important, but the different values themselves are:

  1. Go to Vector.
  2. Choose Analysis Tools.
  3. Select List unique values.
  4. Select a target vector layer and an attribute field.
  5. Click OK to perform the calculation.

It is possible to export the values to the clipboard if they are used in another program (e.g. calculation spread sheet or text editor).

Fig. 101. Basic statistics of a specific vector layer attribute field.

figure101