knitr shows comments from library import

Question

I have a small Rnw file. When compiled with knitr, it shows importing comments in the pdf. How do I remove these comments? Here is the file a.Rnw:

\documentclass[10pt,a4paper]{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\begin{document}
Hi, this is an example!
<<setup, echo=FALSE, cache=TRUE>>==
library(earth, warn.conflicts=FALSE)
a <- rnorm(100); b<- 0.05*rnorm(100) - .2*a
model <- lm(a~b)
plot(model)
@
\end{document}

When I compile with knitr

$ Rscript -e "library(knitr); knit('a.Rnw')"

I get this extraneous bit in the tex file:

\definecolor{shadecolor}{rgb}{0.969, 0.969, 0.969}\color{fgcolor}\begin{kframe}
{\ttfamily\noindent\itshape\color{messagecolor}{\#\# Loading required package: plotmo\\\#\# Loading required package: plotrix}}\end{kframe} 

Which shows up as

Is this normal? How do I remove these comments?

Answer 1

The simplest thing to do is to put message=FALSE in your chunk options, either locally for that chunk or via library(knitr); opts_chunk$set(message=FALSE) near the head of your document.

This is a little bit simpler than the question that @rawr links to in the comments above, because that referred to a badly behaved package that used cat() rather than message() for its startup messages. message=FALSE will suppress all messages produced by the chunk; if you want to be a little bit more precise

suppressPackageStartupMessages(library(earth))

should work, but I find that message=FALSE is usually harmless enough, and looks prettier (e.g. if you wanted echo=TRUE instead).