r - Write latex equation inside knitr chunks -

i trying write equation inside chunk. need use '\sum' r not accept it. got error:

'\s' unrecognized escape in character string 

i tried packages without success.

how can bay pass escape character?

here example:

\documentclass{article}  \begin{document}  <<results='asis',echo=false>>= #library(lazyweave) #library(hwriterplus)  #hwritelatex(as.latex("\bar{r}_{i}=\frac{\sum_{t=1}^{t}{r_{i,t}}}{8}")) # cat('\bar{r}_{i}=\frac{\sum_{t=1}^{t}{r_{i,t}}}{8}')  #cat("$$","\bar{r}_{i}=\frac{\sum_{t=1}^{t}{r_{i,t}}}{8}","$$",sep="")  cat("typically want our paragraphs left justified. expect see when reading.")  @  \end{document} 

edit. read similar examples no 1 involved escape characters.

you need double escape character.

> cat('\\bar{r}_{i}=\\frac{\\sum_{t=1}^{t}{r_{i,t}}}{8}') \bar{r}_{i}=\frac{\sum_{t=1}^{t}{r_{i,t}}}{8}>