[R] looking for a more efficient R code.

[Taka Matzmoto]

Dear R-users

I have four simple linear models, which are all in the form of a*X+b
The estimated parameter vectors are

a <- c(1,2,3,4)
b <- c(4,3,2,1)

My goal is to draw a plot where x-axis is X (range from -100 to 100) and 
y-axis is the sum of
all four linear models

X <- seq(-100,100, length=10000)
plot(X, sum of the four linear functions)

I started with a function for summing

summing <- function(a,b)
{temp <-0;
for (i in 1:length(a))
temp <- temp + a[i]*X+b[i]
}

plot(X, summing(a,b))

I am a R beginner.  I am looking for a more efficient R code.

Any help or advice will be appreciated.

Taka,