library(rbenchmark)
res <- benchmark( cosine(mat),
                  cosineRcpp(mat),
                  columns=c("test", "replications", "elapsed",
                           "relative", "user.self", "sys.self"),
                  order="relative",
                  replications=1000)

res
             test replications elapsed relative user.self sys.self
2 cosineRcpp(mat)         1000 149.974 1.000000   139.389    7.356
1     cosine(mat)         1000 161.268 1.075306   148.613   10.069