I have equations defined likef<-"x^2"and g<-"y^2". I want to obtain equation z like z<-(x^2)*(y^2).
'Class(f)', 'class(g)' and 'class(z)' values doesn`t matter for me.
I tried this:
> f<-"x^2"
> g<-"y^2"
> z<-f*g
I got:
Error in f * g : non-numeric argument to binary operator<br/>
I tried multiplying f<-expression(f) and g<-expression(g) with no result.
I tried also:
> f<-function(x) x^2
> g<-function(y) y^2
> z<-function(x,y) f*g
> z<-parse(text=z)
I got:
Error in as.character(x) :
cannot coerce type 'closure' to vector of type 'character'
With paste(z) instead of parse(z):
> paste(z)
Error in paste(z) :
cannot coerce type 'closure' to vector of type 'character'
Is there a way to do symbolic arithmetics with equations in R without using heavy software like yacas?
You could try the following:
f <- expression(x^2)
g <- expression(y^2)
z <- expression(eval(f) * eval(g))
#> eval(z,list(x = 1, y = 2))
#[1] 4
#...and here's another test, just to be sure:
#> identical(eval(z, list(x = 17, y = 21)), 17^2 * 21^2)
#[1] TRUE
Or you could use the rSymPy package:
library(rSymPy)
x <- Var("x")
y <- Var("y")
sympy("f = x**2")
sympy("g = y**2")
sympy("z = f * g")
#> sympy("z")
#[1] "x**2*y**2"
#> sympy("z.subs([(x,3),(y,2)])")
#[1] "36"
This second suggestion might not be very attractive since it may be easier to use Python directly.