# Description of problem

Hey everyone
I have some experience about coding and building networks but I am new in Brian and brianforum. I’m trying to create a model and I am wanting to use my old input formula because my input should change continuously over time within a certain rule but it seems like I cannot convert that into brianish
There is a basic example of my code. The “t” in example should be the time that used in the operation of the system.
I would be very grateful if someone could help me with that. Thanks !

# Minimal code to reproduce problem

``````def input_pulse():
if t<td1 :
return B0
elif (t >= td1 and t < td2):
if (t < (td1+tp)):
return B1
else:
return B0
elif (t>=td2 and t<(td2+tp)):
return B2
else:
return B0
``````

Hi @SirK , welcome to the Brian’s friends club

So there are a several ways to implement something like that:

1. You can use TimedArray if `td1`, `td2`, `td1+tp`, and `td2+tp` are constant and can be round to an integer of some `dt`. This is a very fast and convenient method to create a stimulus, but it something requires too much memory .
2. If you have a few condition you can implement them as logic expression in the equation for your neurons (see here). Something like that `B0 + (B1-B0)*int( (t>=td1)*(t<(td1+tp)) +(B2-B0)*int( (t>=td2)*(t<(td2+tp)))`. This is also pretty fast.
3. Finally you can use user-provided function which usually slow if written in Python. So this isn’t a best option unless you code it up in Cython or C.

Hope this helps

2 Likes

Let me add one more option: you can use multiple run statements and change the stimulus strength in between. Somethin along the lines of:

``````neurons = NeuronGroup(..., '''dv/dt = ... + I ...''', ...)
I = B0
run(...)
I = B1
run(...)
I = B0
run(...)
I = B2
run(...)
I = B0
run(...)
``````

PS: a minor formatting thing: try to put Python code between triple backticks for nicer display:

`````````
# Here comes the Python code
print('something')
```
``````
1 Like

Thank you so much for your kind responds. It seems like TimedArray will solve my problem

2 Likes