set.seed(9719)                       # this makes the example exactly reproducible
g1 = rnorm( 50, mean=2, sd=2)        # here I generate data w/ different variances
g2 = rnorm(100, mean=3, sd=3)        #   & different sample sizes
my.data = stack(list(g1=g1, g2=g2))  # getting the data into 'stacked' format

library(car)                         # this package houses the function
leveneTest(values~ind, my.data)      # here I test for heteroscedasticity:
# Levene's Test for Homogeneity of Variance (center = median)
#        Df F value   Pr(>F)
# group   1  8.4889 0.004128 **
#       148
# ---
# Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1