AFGEN tables

WOFOST utilizes AFGEN functions for the calculation of the rate of biological processes in response to temperature and development stage.

AFGEN (Arbitrary Function GENerator) is an arbitrary function generator which linearly interpolates between values of a dependent variable, Y, given a value of an independent variable, X, and a table of X and Y data pairs. AFGEN is used at each time step to return values of several functions inherent to mechanistic processes. A plotted example is shown in the Figure below

The table belonging to this example has to be filled as:

Three situations for interpolation can occur:

1) The argument X at which interpolation should take place is less or equal to the first X-value in the table. The Y-value is set to the first Y-value in the table.

2) The argument X value at which interpolation should take place is between the first and the last X-value in the array. The Y-value can now be found via linear interpolation. First the X values top and down from the argument x have to be detected, then the Y-value can be calculated:

3) The argument x at which interpolation should take place is equal to or larger then the last X-value in the array. The Y-value is set to the last Y-value in the array.

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