gwy_derive_units()

gboolean
gwy_derive_units (GwyUnit *unit,
                  GwyDerivedQuantity quantity,
                  gint dimension,
                  GwyUnit *spatial,
                  GwyUnit *value);

Derives units for a known quantity from spatial and value units.

Parameter dimension should be 1 for line data, 2 for images, 3 for volume * data, etc. Some quantities depend on the number of spatial dimensions, for example GWY_DERIVED_PSDF_FULLD or GWY_DERIVED_VARIATION.

Although the units of spatial dimensions can in principle differ, prectically all quantities either do not depend on the spatial units, or cannot be calculated if they differ. So this case is currently not handled.

It is possible to pass NULL for either input unit to mean unitless.

Angles are considered unitless because Gwyddion represents angles in radians by default. Use gwy_derived_quantity_angle_power() to check if a quantity is angle and convert to degrees for the user.

gwy_derived_quantity_spatial_power()

gint
gwy_derived_quantity_spatial_power (GwyDerivedQuantity quantity,
                                    gint dimension);

Reports the power of spatial dimensions in a known quantity.

Note that knowing the power may not be sufficient for correct unit handling. You may also need gwy_derived_quantity_is_angle() and gwy_derived_quantity_same_units().

gwy_derived_quantity_value_power()

gint
gwy_derived_quantity_value_power (GwyDerivedQuantity quantity);

Reports the power of values in a known quantity.

Note that knowing the power may not be sufficient for correct unit handling. You may also need gwy_derived_quantity_is_angle() and gwy_derived_quantity_same_units().

gwy_derived_quantity_angle_power()

gint
gwy_derived_quantity_angle_power (GwyDerivedQuantity quantity);

gwy_derived_quantity_same_units()

gboolean
gwy_derived_quantity_same_units (GwyDerivedQuantity quantity);

Reports whether a derived quantity requires the same spatial and value units.

Some quantities, for example radii of curvature or developed lengths and surface areas, are only meaningful when the values are commensurable with the spatial coordinates.

enum GwyDerivedQuantity

Type of known derived quantity.

Functions such as gwy_derive_units() can be used to generically derive units of known quantities from spatial and value units.

Separate derived quantities exists for a number cases where the derived units must be the same, for example median. rms and value range. This is to improve clarity and make the code more obviously correct. Try to use the exactly matching specific quantity wherever possible. Some are more generic, such as volume or distance, but should still clearly apply to any specific volume or spatial distance.