# Substituting a TaylorN variable into another TaylorN variable

**URL:** <https://discourse.julialang.org/t/substituting-a-taylorn-variable-into-another-taylorn-variable/96014>\
**Category:** General Usage\
**Tags:** question, package, polynomials\
**Created:** [March 13, 2023, 4:43pm UTC](https://discourse.julialang.org/t/substituting-a-taylorn-variable-into-another-taylorn-variable/96014 "2023-03-13T16:43:36Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Vaclav\_Mikeska](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/vaclav_mikeska/32/47661_2.png) [@Vaclav\_Mikeska](https://discourse.julialang.org/u/Vaclav_Mikeska)\
**Post date:** [March 13, 2023, 4:43pm UTC](https://discourse.julialang.org/t/substituting-a-taylorn-variable-into-another-taylorn-variable/96014/1 "2023-03-13T16:43:36Z")

</div>

Let’s have some multivariable polynomials P1 and P2 represented by TaylorN variable from TaylorSeries package, e.g.

```julia
using TaylorSeries

x, y = set_variables("x y")
P1 = TaylorN([HomogeneousPolynomial([1]), HomogeneousPolynomial([2, 3])], 3)
P2 = TaylorN([HomogeneousPolynomial([1]), HomogeneousPolynomial([0, 2])], 3)

```

Then let’s have another polynimial Q in different coordinates, e.g.

```julia
u, v = set_variables("u v")
Q = TaylorN([HomogeneousPolynomial([1]), HomogeneousPolynomial([1, 1])], 3)

```

Now I would like to get from polynomial Q in variables u, v another polynomial in variables x, y by substitution  
u = P1(x,y)  
v = P2(x,y)

Do you have any ideas how to do that? Thanks!