Variation of 'dt'

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magpie
Posts: 23
Joined: Mon Jan 29, 2007 4:13 pm

Variation of 'dt'

Post by magpie »

Hi all,

I have a very basic question of how to change 'dt' in 'RunControl' panel of NEURON GUIs. Currently I am using either Implicit Fixed Step or C-N Fixed Step mode for my simulation and trying to manually change the value of 'dt' to see the effects of varying ‘dt’. I could not change even the default value (i.e. 0.025) of 'dt' in either modes. I might miss something here, but I could not find the way of changing the value of 'dt' anywhere in NEURON website. Is there anybody who can help me? Thanks.
ted
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Re: Variation of 'dt'

Post by ted »

Good question.

dt specifies the integration step size. NEURON's standard run system also has a parameter called steps_per_ms that controls the intervals at which points are plotted to graphs; its numerical value is shown in the field next to the "Points plotted/ms" button. Clearly these two parameters must be compatible, i.e. the interval between two points on a graph must contain a whole number of time steps. The design decision was that steps_per_ms would govern dt. It does this by means of a standard run system procedure called setdt() that adjusts dt as necessary whenever any of the following happens:
--changing the contents of the numerical field next to the "dt" or "Points plotted/ms" button
--calling stdinit()
--calling run()
magpie
Posts: 23
Joined: Mon Jan 29, 2007 4:13 pm

Re: Variation of 'dt'

Post by magpie »

Thank you so much Ted. Your explanation was very helpful to me.
ted
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Re: Variation of 'dt'

Post by ted »

And helpful to others, now that the question & answer are visible to all.
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