Add an plot_label option to plot_grid() about cowplot

[clauswilke]

If I understand correctly, this would add one single label to the entire figure, not each graph in a plot grid, correct? In this case, it's functionality that doesn't belong into plot_grid(), since one might want such a label also on an individual plot. I'll consider adding a convenience function that does this.

[ustervbo]

Yes - it would add a single label to the entire figure.

A convenience function would also work

[clauswilke]

I don't mind adding a convenience function. If you can draft one or prepare a pull request that will increase the likelihood of me adding this quickly.

[ustervbo]

Will this work:

draw_grid_label <- function(label, position = c("top.left", "top", "top.right", "bottom.left", "bottom", "bottom.right"), size, fontface, ...){
  # Get the position
  position <- match.arg(position)

  # Set default font size and face from the theme
  if(missing(size)){
    size <- theme_get()$text$size  
  }
  if(missing(fontface)){
    fontface <- theme_get()$text$face  
  }
  switch(position,
         top.left     = draw_plot_label(label, x = 0,   y = 1, hjust = -0.1, vjust = 1.1,  size = size, fontface = fontface, ...),
         top          = draw_plot_label(label, x = 0.5, y = 1, hjust = 0,    vjust = 1.1,  size = size, fontface = fontface, ...),
         top.right    = draw_plot_label(label, x = 1,   y = 1, hjust = 1.1,  vjust = 1.1,  size = size, fontface = fontface, ...),
         bottom.left  = draw_plot_label(label, x = 0,   y = 0, hjust = -0.1, vjust = -0.1, size = size, fontface = fontface, ...),
         bottom       = draw_plot_label(label, x = 0.5, y = 0, hjust = 0,    vjust = -0.1, size = size, fontface = fontface, ...),
         bottom.right = draw_plot_label(label, x = 1,   y = 0, hjust = 1.1,  vjust = -0.1, size = size, fontface = fontface, ...)
  )
}

[clauswilke]

I think so. Could you write the required documentation as well, preferably including some examples? Thanks!

[ustervbo]

A little late, but here it is:

#' Add a label to a grid
#' 
#' @description 
#' Add a label to a grid
#'
#' @param label Label to be drawn
#' @param position Position of the label, can be one of "top.left", "top", "top.right", "bottom.left", "bottom", "bottom.right". Default is "top.left"
#' @param size (optional) Size of the label to be drawn. Default is the text size of the current theme
#' @param fontface (optional) Font face of the label to be drawn. Default is the font face of the current theme
#' @param ... other arguments passed to \code{draw_plot_label}
#'
#' @examples
#' 
#' p1 <- qplot(1:10, 1:10)
#' p2 <- qplot(1:10, (1:10)^2)
#' p3 <- qplot(1:10, (1:10)^3)
#' p4 <- qplot(1:10, (1:10)^4)
#' 
#' # Create a simple grid
#' p <- plot_grid(p1, p2, p3, p4)
#' 
#' # Default font size and position
#' p + draw_grid_label(label = "Figure 1")
#' 
#' # Different position and font size
#' p + draw_grid_label(label = "Figure 1", position = "bottom.right", size = 10)
#' 
#' # Using bold font face
#' p + draw_grid_label(label = "Figure 1", fontface = "bold")
#' 
#' # Making the label red and slanted
#' p + draw_grid_label(label = "Figure 1", angle = -45, colour = "red")
#' 
#' @author Ulrik Stervbo (ulrik.stervbo [AT] gmail.com)
#' 
draw_grid_label <- function(label, position = c("top.left", "top", "top.right", "bottom.left", "bottom", "bottom.right"), size, fontface, ...){
  # Get the position
  position <- match.arg(position)

  # Set default font size and face from the theme
  if(missing(size)){
    size <- theme_get()$text$size  
  }
  if(missing(fontface)){
    fontface <- theme_get()$text$face  
  }

  # Call draw_plot_label() with appropriate label positions
  switch(position,
         top.left     = draw_plot_label(label, x = 0,   y = 1, hjust = -0.1, vjust = 1.1,  size = size, fontface = fontface, ...),
         top          = draw_plot_label(label, x = 0.5, y = 1, hjust = 0,    vjust = 1.1,  size = size, fontface = fontface, ...),
         top.right    = draw_plot_label(label, x = 1,   y = 1, hjust = 1.1,  vjust = 1.1,  size = size, fontface = fontface, ...),
         bottom.left  = draw_plot_label(label, x = 0,   y = 0, hjust = -0.1, vjust = -0.1, size = size, fontface = fontface, ...),
         bottom       = draw_plot_label(label, x = 0.5, y = 0, hjust = 0,    vjust = -0.1, size = size, fontface = fontface, ...),
         bottom.right = draw_plot_label(label, x = 1,   y = 0, hjust = 1.1,  vjust = -0.1, size = size, fontface = fontface, ...)
  )
}

Let me know if there are any problems

[clauswilke]

Thanks. I'm extremely busy right now, but I've added this to the TODO list and I'll get to it eventually.

[clauswilke]

This is now on github and will be part of the next release. Note that I changed the name of the function to draw_figure_label since the function is not specific to plot grids and works on individual figures as well.

[clauswilke]

This is on CRAN now.