**var_delay** function

var_delay(var,n)

Input: a variable name and a numerical value (real or integer) of time units

Result: the value (any type) of the named variable, n time units ago

This function returns some previous value of another variable, an arbitrary period of time before. The period of time is defined in time units (not steps). The number need not be an integer, but whatever the actual time step, delay is always rounded to the nearest multiple of 0.1 of a time unit. The variable whose previous value is required is specified by name. The variables must be linked with an influence arrow.

This is a general replacement for the last( ) function, which returns the value of the named variable from the previous time step only. The delay must be between 0 and 100 and is rounded to the nearest 0.1. The delay can vary; if the delay is constant, the function const_delay() will do the job more efficiently.

Examples:

runoff=var_delay(rain,soak_time)

In: Contents >> Working with equations >> Functions >> Built-in functions