Calculated Data Column

A calculated data column is a data column defined by some mathematical definition, and dynamically recalculated whenever necessary. A calculated data column is the opposite of a static data column.

In the screenshot below for example, a calculated data column is defined as the average of two other data columns:

To add a calculated column to your dataset, click Add Column in the Data Columns tab of the Configure Dataset window:

The list of data columns that appears in the Configure Dataset window displays a small calculator icon beside calculated data columns:

User-Generated Calculated Data Columns

You can create the following types of calculated data columns:

Calculated Data Column Class	Description
Combine Columns	Combine specific data columns, or an entire data column type using: average, median, primary/backup, maximum, minimum, sum, difference, absolute difference, ratio, product
Wind Shear Parameter	Change in wind speed with height above ground using the log law (surface roughness) or the power law (power law exponent)
Speed SD Shear Exponent	Power law exponent fitted to wind speed SD data, indicating how speed SD changes with height
Wind Veer Rate	Measure of how quickly the wind direction changes with height above ground
Temperature gradient	Calculated rate at which temperature changes with height
Density-Adjusted Wind Speed	The wind speed that gives the same wind power density at a specific target air density as the actual measured wind speed at the actual air density.
Rotor-Equivalent Wind Speed	The area-weighted average wind speed across the wind turbine rotor disk
Moving Average	Moving or running average of single data column
Accumulation	Cumulative sum of a data column over a period of time
Polynomial Function	Create a new data column based on a polynomial function applied to an existing data column
Piecewise Linear Function	Create a new data column by applying a piecewise linear function to an existing data column
Solar Variables	Calculated data about the angle of the sun, solar radiation and other variables relevent to solar power
Date/Time Variables	Hour of day, day of week, day of year, or week of year.
Reconstruct and average	Combines two speed columns by averaging, first reconstructing missing values using linear regression by sector
Reconstruct and average SD/Max	Combines two speed SD or max columns by averaging, with special consideration of time steps requiring reconstruction of a speed value
Combine by Boom Orientation	Create a mean wind speed column by combining two other wind speed columns by boom orientation.
Inflow Angle	Inflow angle of the wind using specified horizontal and vertical wind speeds.
Dew Point	The dew point based on the temperature and relative humidity.
First Difference	Compare the value of a data column to the value in the previous time step.
Energy-Weighted Air Density	The air density multiplied by wind power density, divided by mean wind power density.

Automatically Generated Calculated Data Columns

In some situations, Windographer will automatically generate one or more calculated data columns:

Calculated Column	Notes
Air density	This column's properties window let you specify settings related to relative humidity and flagging.
Turbulence intensity	Generated for every wind speed data column that has an associated SD data column. The properties window lets you decide whether to apply turbulence detrending.
Wind power density	Generated for every wind speed data column.
Ratio of colocated wind speed sensors	Generated if you request so in Tools > Options > General.

Properties of Calculated Data Columns

Calculated data columns are always up-to-date. Whenever you change a data column in any way, Windographer regenerates any affected calculated data columns.
Calculated data columns do not increase the size of your .windog files, but they do increase Windographer's memory usage and computation time.
When generating calculated data columns, in most cases Windographer uses default flag filtering, but in some cases (turbulence intensity, wind power density) the calculated column inherits flagged segments from its precursor data columns.
You cannot apply flags to a calculated data column, whether manually or using a flag rule.
You cannot scale, calibrate, time shift, or fill gaps in a calculated data column.
You can refer to calculated data columns in the search criteria of flag rules.
You cannot append a calculated column from one file to another.

In the Data Columns tab of the Configure Dataset window you can convert calculated data columns to static data columns using the Convert to Static Column(s) button, or create static copies of calculated data columns using the Copy Column(s) button.