### Obtaining NetCon actual pre-section along fraction x value?

Posted:

**Mon Jan 22, 2018 4:47 pm**Given a NetCon instance whose source is section membrane potential, is it possible to extract the actual x value location on the pre-section?

For example, the following minimal python code only returns either 0, 0.5, or 1.0 fractions.

I understand this is due to a warning mentioned in the documentation:

https://neuron.yale.edu/neuron/static/p ... Con.preloc

Note: In my use case, I'm comparing a sizable number of models created by others, and modifying the original models to keep track of the along fractions would not be practical.

For example, the following minimal python code only returns either 0, 0.5, or 1.0 fractions.

Code: Select all

```
from neuron import h, gui
soma = h.Section()
soma.nseg = 10
h.NetCon(soma(0)._ref_v,None).preloc() # OK - returns 0
h.NetCon(soma(1)._ref_v,None).preloc() # OK - returns 1.0
h.NetCon(soma(0.5)._ref_v,None).preloc() # OK - returns 0.5
h.NetCon(soma(0.25)._ref_v,None).preloc() # Problem - returns 0.5 instead of 0.25
h.NetCon(soma(0.75)._ref_v,None).preloc() # Problem - returns 0.5 instead of 0.75
```

https://neuron.yale.edu/neuron/static/p ... Con.preloc

Given the above limitation of preloc(), is there any other way to obtain the actual along pre-section fraction that was originally used when creating the NetCon instance?Warning: The return value of x is .5 unless the source is a membrane potential and located at 0, or 1, in which case value returned is 0 or 1, respectively. Therefore it does not necessarily correspond to the actual x value location.

Note: In my use case, I'm comparing a sizable number of models created by others, and modifying the original models to keep track of the along fractions would not be practical.