add echo=FALSE to the r chunk. It will remove the evaluated code inside the chunk. Also you can add message=FALSE, and warning=FALSE to not show messages and warnings.

Example (It will plot the chart and not show the code, warnings and messages).

```{r, echo=FALSE,warning=FALSE,message=FALSE}
plot(iris)
```

I am doing the knitting of my code to produce a html file. I got it but next to the graphs it also display some boxes with information about i.e. line, color, text and so on. Is it possible not to see that information in my html file?