# Using Symbolics and Flux
**URL:** https://discourse.julialang.org/t/using-symbolics-and-flux/89498
**Category:** Modelling & Simulations
**Created:** [October 29, 2022, 5:20pm UTC](https://discourse.julialang.org/t/using-symbolics-and-flux/89498 "2022-10-29T17:20:23Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Max\_Beez](https://discourse.julialang.org/u/Max_Beez)
#### Post date: [October 29, 2022, 5:20pm UTC](https://discourse.julialang.org/t/using-symbolics-and-flux/89498/1 "2022-10-29T17:20:23Z")
Let’s say I have something along the lines of
> using Symbolics, Flux
> @variables x,y
> function f()
> [x^2y^3 ; x+y^2]
> end
> grad\_f(x,y) = Flux.gradient(transpose(f())\*f(), x,y)
> display(grad\_f(x,y))
The following error comes:
> ERROR: Sym x^(4(y^3)) + (x + y^2)^2 is not callable. Use @syms x^(4(y^3)) + (x + y^2)^2(var1, var2,…) to create it as a callable.
However it isn’t clear how I use “Use @syms x^(4(y^3)) + (x + y^2)^2(var1, var2,…)”. That is I am not sure where I include this or the syntactical formatting necessary.
[https://docs.juliahub.com/Symbolics/eABRO/3.4.0/tutorials/symbolic\_functions/#Syms-and-callable-Syms-1](https://docs.juliahub.com/Symbolics/eABRO/3.4.0/tutorials/symbolic_functions/#Syms-and-callable-Syms-1)
Additionally if I use
> grad\_f(x,y) = Symbolics.gradient(transpose(f())\*f(), [x,y])
method I always get a zero vector returned. Namely, it returns
> 2-element Vector{Num}:
> 0
> 0
---
### Author:  [@Tomas\_Pevny](https://discourse.julialang.org/u/Tomas_Pevny)
#### Post date: [October 29, 2022, 6:01pm UTC](https://discourse.julialang.org/t/using-symbolics-and-flux/89498/2 "2022-10-29T18:01:53Z")
I am afraid Symbolics and Flux are not compatible.
---
### Author:  [@Max\_Beez](https://discourse.julialang.org/u/Max_Beez)
#### Post date: [October 29, 2022, 6:33pm UTC](https://discourse.julialang.org/t/using-symbolics-and-flux/89498/3 "2022-10-29T18:33:04Z")
This is false given I just managed to get the following to work:
> using Symbolics, Flux
> @variables x,y,z
> function ff(x,y,z)
> x^2+y^2\*z
> end
> grad\_ff(x,y,z) = Flux.gradient(ff, x,y,z)
the output is:
> (2x, 2y\*z, y^2)
---
### Author:  [@Max\_Beez](https://discourse.julialang.org/u/Max_Beez)
#### Post date: [October 29, 2022, 6:48pm UTC](https://discourse.julialang.org/t/using-symbolics-and-flux/89498/4 "2022-10-29T18:48:21Z")
I found a fix, consider the following MWE
> using Symbolics, Flux
@variables x, y
function f(x,y)
A = transpose([x;y])\*[x;y]
return A[1]
end
display(f(x,y))
This returns
> x^2 + y^2
Then if I add
> Flux.gradient(f,x,y)
it returns
> (2x, 2y)
Which is correct. Seems I was using incorrect syntax for what I wanted.
---
### Author:  [@ToucheSir](https://discourse.julialang.org/u/ToucheSir)
#### Post date: [October 29, 2022, 7:02pm UTC](https://discourse.julialang.org/t/using-symbolics-and-flux/89498/5 "2022-10-29T19:02:42Z")
Note that Flux reexports `gradient` from Zygote.jl, so unless you need the NN functionality I’d recommend using that instead.