SMS:Dataset Toolbox: Difference between revisions

Revision as of 19:48, 1 June 2009

The Data Set Toolbox contains numerous tools for working with data sets. Once the options for the current tool have been set and a name for the resulting data set has been specified, selecting the Compute, Sample, etc. button will create the new data set. The name of the new data set will appear in the list of data sets.

The Data set Toolbox tools are organized as follows:

Temporal

Sample Times

Create a new data set from sampled times of an existing data set. If "Interpolate times" is selected, linear interpolation will be used to determine the sampled times. If "Interpolate times" is not selected, the value from the nearest existing data set time step will be used.

Derivatives

Create a new data set of the change from one time step to the next, or the derivative from one time step to the next of an existing data set. When computing a derivative, the time units must be specified. The the new data set will output data in between the existing data set time steps, resulting in one fewer time step than the original data set.

Math

Compare

Compare two data sets by subtracting the "Alternate" data set from the "Base" data set. User specified NULL values are assigned if the base or alternate data set is inactive.

Data Calculator

For more information, see Data Calculator.

Spatial

Geometry

Grid Spacing: Creates a function that gives the average distance between a node and its neighbors.
Gradient: Creates a function that gives the gradient at each node. The gradient is calculated as the run divided by the rise.
Gradient Angle: Creates a function that gives the direction in degrees of the maximum gradient at each point.
Directional Derivative: Creates a vector function that gives the gradient (run/rise) in the x and y directions.

Smoothing Data Sets

For more information, see Smooth Data Set.

Conversion

Scalar to Vector

Converts two scalar data sets to a single vector data set. The specified scalar data sets can be either magnitude and direction or x and y components.

Vector to Scalar

Converts a single vector data set into two scalar data sets. The resulting scalar data sets can be either magnitude and direction or x and y components.

Coastal

Local wavelength/celerity

Creates two functions that calculate the celerity and wavelength at each node for any depths.

Celerity = (Gravity * Nodal Elevation)^0.5.
Wavelength = Period * Celerity.

Gravity Waves (Courant or Timesteps)

Creates a function that gives the courant number for each node given the Timestep, or the gravity wave timestep given the Courant Number.

Courant Number = Timestep * (Gravity * Nodal Elevation)^0.5 / Nodal Spacing.
Timestep = Courant Number * Nodal Spacing / (Gravity * Nodal Elevation)^0.5.

Advective (Courant or Timesteps)

Advective requires a vector function as input and is disabled if no vector functions exist. The courant option creates a function that calculates the courant number given the Timestep and a velocity function. The timestep option creates a function that calculates the timestep given the Courant Number and a velocity function.

Courant Number = Nodal Velocity Magnitude * Timestep / Nodal Spacing.
Timestep = Courant Number * Nodal Spacing / Nodal Velocity Magnitude.

Modification

Map Activity

This maps the activity array from one data set to second data set. This may be used to show only the values of interest on a particular data set. This operation creates a new data set.

Filter

This creates a new data set based on specified criteria. The following options are available for filtering:

< (less than)
<= (less than or equal to)
> (greater than)
>= (greater than or equal to)
equal
not equal
null
not null

If the value passes the specified filter, the following can be assigned:

original (no change)
specify (a user specified value)
null (the data set null value)
true (1.0)
false (0.0)
time - The first time the condition was met. Time can be specified in seconds, minutes, hours or days, and includes fractional values (such as 3.27 hours).

In addition, if the value passes none of the criteria, a default value can be assigned (see available options above).

The filtering is applied in the order specified. This means as soon as the new data set passes a test, it will not be filtered by subsequent tests.