如何对 R 中的数学表达式求平方？

Question

I have a mathematical expression which is;

> myexp <- expression(x^2 + 2*x + 1)
> 
> myexp

expression(x^2 + 2 * x + 1)

I'd like to square the expression but it doesn't work when I run myexp**2 or myexp^2

What I want to obtain is this;

expression(x^4 + 4 * x^3 + 6 * x^2 + 4 * x + 1)

how can we do this in R?

Thanks in advance.

Answer 1

"Expressions" in R are not mathematical expressions, but rather lists of calls, symbols, etc. See the help file for ?expression .

For what you want to accomplish, I believe you need the polynom package.

myexp <- polynom::polynomial(c(1,2,1))
myexp^2

## 1 + 4*x + 6*x^2 + 4*x^3 + x^4 

Answer 2

One option is the Ryacas package, which will work with multiple variables:

Ryacas::yac_expr("Expand((x^2 + y^2 + 3*x + 3)^2)")
#> expression(x^4 + 6 * x^3 + (2 * y^2 + 15) * x^2 + (6 * y^2 + 
#>     18) * x + y^4 + 6 * y^2 + 9)