# Polynomial transposition

Let's say I have

```
R1 = ZZ['y']['x']
R2 = ZZ['x']['y']
```

Is there a builtin function in Sage for converting an element from R1 to R2 by transposing the coefficients, not just switching the variables? For instance `y*x+y`

should become `(x+1)*y`

, not `x*y+x`

.

I can do it by first coercing to `ZZ['x','y']`

and then to `R2`

, but that seems clumsy (and possibly inefficient). I could also just write a loop, but that seems ugly (and again possibly inefficient). It would be fine with a function that just transposes the polynomial within `R1`

(then I can just coerce the result to `R2`

afterwards).