R-create and assign multiple variables from an input vector using loops within a function

Question

I need to optimize multiple objective expressions based on a data frame (i.e., coef.opti).

coef.opti = data.frame(Compound = paste("Compound",1:4,sep=""),
                       Ingredient1 = c(36.6, 20.8, 109.6, 7.6),
                       Ingredient2 = c(-7.6,-6.3,-82.2,11.2),
                       Ingredient3 = c(-7.6,3.8,-14,5.2))

The function can be written manually as fun1.

fun1 = function(x) {x1=x[1] 
                    x2=x[2] 
                    x3=x[3] 
                    y = numeric(4) 
                    y[1] = abs((36.6)*x1+(-7.6)*x2+(-7.6)*x3) 
                    y[2] = abs((20.8)*x1+(-6.3)*x2+(3.8)*x3)
                    y[3] = abs((109.6)*x1+(-82.2)*x2+(-14)*x3)
                    y[4] = abs((7.6)*x1+(11.2)*x2+(5.2)*x3)
                    return(y)
                    }

But this is time consuming and changing the number of variables or expressions needs re-writing the xs and ys. Can the function be written with for loops or something alike?

For instance, for the x vector, I want to replace

x1 = x[1]
x2 = x[2]
x3 = x[3] 

with a loops so that a specified number of variables are created and assigned accordingly and automatically within the function.

The following is what I have so far. But I couldn't get it work.Take 3 variables as an example.

(a = paste("x",1:3,"<-","x[",1:3,"]",sep="",collapse=";"))
 noquote(a)

The output looks like this.

[1] x1<-x[1];x2<-x[2];x3<-x[3]
 

But this is a "noquote," not three separate statements assigning elements of a vector to different variables.

> class(noquote(a))
  [1] "noquote"

> is.vector(noquote(a))
  [1] FALSE

> typeof(noquote(a))
  [1] "character"

I also tried the function cat(). But it prints out.

fun1 = function(x) {
                    cat(paste("x",1:3," <-,"x[",1:3,"]",sep=""),sep="\n")
                    y = numeric(4) 
                    y[1] = abs((36.6)*x1+(-7.6)*x2+(-7.6)*x3) 
                    y[2] = abs((20.8)*x1+(-6.3)*x2+(3.8)*x3)
                    y[3] = abs((109.6)*x1+(-82.2)*x2+(-14)*x3)
                    y[4] = abs((7.6)*x1+(11.2)*x2+(5.2)*x3)
                    return(y)
                    }

 > cat(paste("x",1:3," <- ","x[",1:3,"]",sep=""),sep="\n")
   x1 <- x[1]
   x2 <- x[2]
   x3 <- x[3]

The cat() produce the expected except that it prints out.

Similarly, I hope to write the 4 expressions (i.e., y) by looping. Any advice is greatly appreciated!