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Mathematical expressions in R plot

Mathematical anotations to R plots can be formated LaTeX style with the expression function. The expression() can be included in

  • plot titles 
    title( expression(...))
  • axis anotations 
    plot( ... , xlab = expression(...))

    or

  • the plot panel itself 
    text( x , y , expression(...))

An example:

plot( 0 , 0 , type = "n" , xlab = expression( "Nothing" * (mu*mol/l)) )
text( 0 , 0 , expression(beta>=0.2))
title( expression( "Only an expression() demo " * theta^(2*pi)))

It is even possible to update the plot anotation from a variable (found on the R forum)

[R] Expression in plot text

Roger Koenker roger at ysidro.econ.uiuc.edu
Wed Dec 6 20:22:05 CET 2000 

expression(paste(hat(theta),'= ',that)))

We’ve been here before. To get an expression either use parse on your
pasted character string or substitute on an expression. There are worked
examples in the list achives. The neatest is

title(substitute(hat(theta) == that, list(that=that)))

(note it is == not =)

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Declare character encoding in HTML

Writing documents in english, german and norwegian leaves you with a mess of different character encodings in documents and also webpages.

Just wrote a plain HTML page with norwegian special characters and Firefox, did not show the characters correctly, so I had to find out how to specify that the encoding of the norwegian æøå’s is UTF-8.

Fortunately there is a good explanation on the W3C Blog.

The code to specify the encoding is

http-equiv="Content-Type" content="text/html; charset=UTF-8"

I have no illusion about some browser (IE?) getting it wrong anyway. At least Firefox seems to comply…