inst/resources/scripts/quad2.r

In spuRs: Functions and Datasets for "Introduction to Scientific Programming and Simulation Using R"

# program spuRs/resources/scripts/quad2.r
# find the zeros of a2*x^2 + a1*x + a0 = 0

# clear the workspace
rm(list=ls())

# input
a2 <- 1
a1 <- 4
a0 <- 5

# calculate the discriminant
discrim <- a1^2 - 4*a2*a0
# calculate the roots depending on the value of the discriminant
if (discrim > 0) {
    roots <- c( (-a1 + sqrt(a1^2 - 4*a2*a0))/(2*a2),
               (-a1 - sqrt(a1^2 - 4*a2*a0))/(2*a2) )
} else {
    if (discrim == 0) {
        roots <- -a1/(2*a2)
    } else {
        roots <- c()
    }
}

# output
show(roots)