title: Reduced major axis line and CI for ggplot in R
body: <p>Is there anyway to add a reduced major axis line (and ideally CI) to a ggplot? I know I can use method="lm" to get an OLS fit, but there doesn't seem to be a default method for RMA. I can get the RMA coefs and the CI interval from package lmodel2, but adding them with geom_abline() doesn't seem to work. Here's dummy data and code. I just want to replace the OLS line and CI with a RMA line and CI:</p>
  
  <pre><code>dat &lt;- data.frame(a=log10(rnorm(50, 30, 10)), b=log10(rnorm(50, 20, 2)))
  
  ggplot(dat, aes(x=a, y=b) ) + 
      geom_point(shape=1) +       
      geom_smooth(method="lm") 
  </code></pre>
  
  <p>Edit1: the code below gets the RMA (here called SMA - standardized major axis) coefs and CIs. Package lmodel2 provides more detailed output, while package smatr returns just the coefs and CIs, if that's any help:</p>
  
  <pre><code>library(lmodel2)
  fit1 &lt;- lmodel2(b ~ a, data=dat)
  
  library(smatr)
  fit2 &lt;- line.cis(b, a, data=dat)
  </code></pre>