Flag Rule

A flag rule is a set of instructions that tell Windographer to apply a certain flag to certain data columns under certain conditions. When you execute a flag rule, Windographer searches through the dataset and applies the specified flag wherever it finds those conditions.

A flag rule might, for example, apply the 'Low Temperature' flag to all wind speed sensors whenever a temperature sensor drops below -15°C. Or it could apply the 'Tower Shading' flag to a particular wind speed sensor whenever the wind direction falls within a particular range.

You can define and execute flag rules in the Flag With Rules window. In the Flag Tower Shading window, Windographer automatically generates rules to flag tower shading events.

The article on flag rule examples provides several examples.

Tip: You can apply flags manually instead of using flag rules, but rules can save a lot of time in cases where you can describe mathematically the conditions under which you want to apply the flag.

You can specify one or more data columns to search for high or low values, or rapidly changing values, or whatever behavior interests you. When searching those data columns, Windographer makes use of default flag filtering. For example, imagine that you write a flag rule that searches for high values of temperature, but the data logger recorded occasional values of 9999 for temperature to indicate missing measurements or some error condition. If you first flag those 9999 values as invalid, then they will not trigger your high temperature flag rule. The high temperature flag rule will ignore any temperature values that are flagged to exclude.