3 replies to this topic

[Jun Shen]

Hi,

 

I wonder if there is anyway to define a lag time in the differential equations? Thanks.

 

Jun

[Simon Davis]

Hi Jun, If you're looking to write your own models I really suggest you look at the new Phoenix model engine since in addition to richer options for built-in models and the Graphical model designer; it also has a text model editor that will highlight typos/options for you;

Simon

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[Jun Shen]

Hi, Simon,

 

I believe eventually we will. It's just a matter of timing issue as the validation is kind of big deal. But the question is still here: does Phoenix support delayed differential equations? If not, what is the workaround?

 

Jun

[Martin Beliveau]

Jun,

 

In ASCII code, lag time in DE were handled in the form of "if, then" statements relating the time variable defined as X. See PD14 in Weiner and Gabrielsson (4th Ed).

 

PHX handles time in DE through the use of the sleep statement through a sequence block, which is an elegant way of handling the unstability of the if then statements. Syntax in PML is:

 

    sequence{"initialize"

        sleep("whatever")

         "switch on"

        }

Keeping PD14 as an example, the code in PML would look like:

    sequence{E1 = Kin / Kout

         E2 = Kin / Kout

         ACTH = 1

        sleep(T1)

         ACTH = 2^n

        sleep(T2)

         ACTH = 1

        }

This allows you to turn compartments on and off by changing the appropriate switch following the sleep time.

 

martin