# Quantities

A quantity is a value that is calculated at each point for each axis in a DataSet. More than one quantity can be calculated for any position on the axes and each one typically represents a different type or component of a result.

For example, the ${E}_{x}$ , ${E}_{y}$ and ${E}_{z}$ components of an electric near field would be stored as three separate complex quantities. All of these quantities are valid at the same physical position and frequency. Looking again at the near field example of a horn antenna, the structure of Quantities are illustrated.

nf = pf.NearField.GetDataSet("Horn.StandardConfiguration1.NearField1")
for index, quantity in pairs(nf.Quantities) do
print(string.format("quantity[%d]: '%s' is a %s quantity that is measured in '%s'",
index,
quantity.Name,
quantity.QuantityType,
quantity.Unit))
end
quantity[1]: ' EFieldComp1 ' is a Complex quantity that is measured in ' V/m '
quantity[2]: ' EFieldComp2 ' is a Complex quantity that is measured in ' V/m '
quantity[3]: ' EFieldComp3 ' is a Complex quantity that is measured in ' V/m '
quantity[4]: ' HFieldComp1 ' is a Complex quantity that is measured in ' A/m '
quantity[5]: ' HFieldComp2 ' is a Complex quantity that is measured in ' A/m '
quantity[6]: ' HFieldComp3 ' is a Complex quantity that is measured in ' A/m '
quantity[7]: ' MediumIndex ' is a Scalar quantity that is measured in ''

The quantities contained in this near field are the three components of both the electric and magnetic field. These values are specified at every dimension for the specified Axes values. In order to specify a near field component, complex values must be used. The units are specified as $\frac{V}{m}$ for the electric near field components and $\frac{A}{m}$ for the magnetic components. If we were to inspect the entire DataSet , a single data point would then contain values for each of the seven quantity fields stored in the DataSet.

A DataSet may contain any quantity. However, if the DataSet is to be used as an internal type, the minimum quantities required for POSTFEKO to interpret the data correctly must be present. For instance, a near field must contain either a complete set of electric field components or a complete set of magnetic field components in order to be valid. This restriction only applies to a DataSet that will be used as though it is a near field calculated by the Feko kernel.