title: R - how to add scale functio to a theme object in ggplot2?
body: <p>I am trying to prepare a custom theme for <code>ggplot</code> in order not to copy-paste the theme all the time. I stacked on an issue that I can not add <code>scale</code> functions to <code>theme</code> object. Does anyone know how this should be solved?</p>
  
  <pre><code> library(ggthemes)
   theme_RTCGA &lt;- function(base_size = 11, base_family = "", ...){
  
      theme_pander(gm = TRUE, gM = TRUE, ...) %+replace%
          theme(panel.grid = element_line(), 
                      panel.grid.major = element_line(colour = "grey90", size = 0.2),
                      panel.grid.minor = element_line(colour = "grey98", size = 0.5),
                      legend.position = "top") + 
    scale_colour_pander() +
    scale_fill_pander()
   }
  
   library(ggplot2)
   # plot
   df &lt;- data.frame(gp = factor(rep(letters[1:3], each = 10)),
                                   y = rnorm(30))
   ds &lt;- plyr::ddply(df, "gp", plyr::summarise, mean = mean(y), sd = sd(y))
   ggplot(df, aes(x = gp, y = y)) +
      geom_point() +
      geom_point(data = ds, aes(y = mean),
                           colour = 'red', size = 3) + theme_RTCGA()
  Error: Don't know how to add scale_colour_pander() to a theme object
  </code></pre>