The knitr package (Xie 2016) is an alternative tool to Sweave based on a different design with more features. This document is not an introduction, but only serves as a placeholder to guide you to the real manuals, which are available on the package website https://yihui.org/knitr/1, and remember to read the help pages of functions in this package. There is a book (Xie 2015) for this package, but it may not be useful to those who prefer digging out information on the web.
Anyway, here is a code chunk that shows you can compile vignettes with knitr as well using R 3.0.x, which supports non-Sweave vignettes:
options(digits = 4) rnorm(20)
##  -0.432492 -1.934594 0.090109 -0.537050 0.349098 0.156540 -0.202615 ##  -2.024916 -0.940910 0.602132 0.624322 -0.422067 -0.706236 -1.168691 ##  -0.481862 0.272402 -0.528331 -0.497320 -0.008859 -1.556787
= lm(dist ~ speed, data = cars) fit = coef(fit)b
|Estimate||Std. Error||t value||Pr(>|t|)|
The fitted regression equation is \(Y=-17.5791+3.9324x\).
par(mar=c(4, 4, 1, .1)) plot(cars, pch = 20) abline(fit, col = 'red')