Regression

regression.R

# GET EQUATION AND R-SQUARED AS STRING
# SOURCE: http://goo.gl/K4yh

lm_eqn = function(df){
    m = lm(y ~ x, df);
    eq <- substitute(italic(y) == a + b %.% italic(x)*","~~italic(r)^2~"="~r2, 
         list(a = format(coef(m)[1], digits = 2), 
              b = format(coef(m)[2], digits = 2), 
             r2 = format(summary(m)$r.squared, digits = 3)))
    as.character(as.expression(eq));                 
}

p1 = p + geom_text(aes(x = 25, y = 300, label = lm_eqn(df)), parse = TRUE)