# Normalizing a transfer function
**URL:** https://discourse.julialang.org/t/normalizing-a-transfer-function/104834
**Category:** Modelling & Simulations
**Tags:** question, control, controlsystems
**Created:** [October 11, 2023, 8:04am UTC](https://discourse.julialang.org/t/normalizing-a-transfer-function/104834 "2023-10-11T08:04:51Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@ufechner7](https://discourse.julialang.org/u/ufechner7)
#### Post date: [October 11, 2023, 8:04am UTC](https://discourse.julialang.org/t/normalizing-a-transfer-function/104834/1 "2023-10-11T08:04:51Z")
Is there already a function to normalize a transfer function?
I have:
```julia
TransferFunction{Continuous, ControlSystemsBase.SisoRational{Float64}}
-951.729934283765s^2
---------------------------------------------------------------------------------------
3.1777394243568e7s^3 + 7.907227012152197e6s^2 + 540639.1480777722s + 5918.8473721761775
```
and I would like all coefficients to be divided by -951.729934283765.
---
### Author:  [@ufechner7](https://discourse.julialang.org/u/ufechner7)
#### Post date: [October 11, 2023, 9:11am UTC](https://discourse.julialang.org/t/normalizing-a-transfer-function/104834/2 "2023-10-11T09:11:45Z")
OK, wrote a function that does this myself:
```julia
function normalize(tf_::TransferFunction{Continuous, ControlSystemsBase.SisoRational{Float64}})
expr = tf_.matrix[1]
factor = expr.num.coeffs[end]
if factor == 0.0
return tf_
end
tf(reverse(expr.num.coeffs./factor), reverse(expr.den.coeffs./factor))
end
```
---
### Author:  [@baggepinnen](https://discourse.julialang.org/u/baggepinnen)
#### Post date: [October 11, 2023, 9:15am UTC](https://discourse.julialang.org/t/normalizing-a-transfer-function/104834/3 "2023-10-11T09:15:15Z")
You are reaching deep into the internals of ControlSystems here. See the functions `numvec` and `denvec` which would make your implementation simpler and avoid using internals.
> [@ufechner7](#):
>
> Is there already a function to normalize a transfer function?
No, because there are many possible ways one could possibly normalize a transfer function, and different people prefer different conventions.
---
### Author:  [@ufechner7](https://discourse.julialang.org/u/ufechner7)
#### Post date: [October 11, 2023, 10:20am UTC](https://discourse.julialang.org/t/normalizing-a-transfer-function/104834/4 "2023-10-11T10:20:24Z")
Thank you!