Panel Grid Aesthetics Can't be Changed for theme_classic

[DarioS]

It has no effect for theme_classic

ggplot(mtcars, aes(wt, mpg)) + geom_point() + theme_classic() + theme(panel.grid.major.y = element_line(colour = "pink", size = 4))

but it does work for the other themes

ggplot(mtcars, aes(wt, mpg)) + geom_point() + theme_bw() + theme(panel.grid.major.y = element_line(colour = "pink", size = 4))

It also doesn't work for the grid lines perpendicular to the x-axis.

[Katiedaisey]

Since panel.grid.major.y inherits from panel.grid.major while the later has an element_blank class, it will not inherit the desired element_line. This can easily be confirmed via

calc_element('panel.grid.major.y', theme_classic() + theme(panel.grid.major.y = element_line(colour = "pink", size = 4)), verbose = T)

This will happen whenever a new element inherits from a element that was declared blank in the base theme. For instance, adding tick marks only on x with theme_minimal also fails:

ggplot(mtcars, aes(wt, mpg)) + geom_point() + theme_minimal() + theme(axis.tick.x = element_line(colour = "pink", size = 4))

It seems these might actually not work in only three cases in which case I would suggest just updating the two themes, classic and minimal, by declaring the problem children.

theme_classic2 <- function(base_size = 12, base_family = ""){
  theme_bw(base_size = base_size, base_family = base_family) %+replace%
    theme(
      panel.border     = element_blank(),
      axis.line        = element_line(colour = "black"),
      panel.grid.major = element_line(),
      panel.grid.major.x = element_blank(),
      panel.grid.major.y = element_blank(),
      panel.grid.minor = element_blank(),
      panel.grid.minor.x = element_blank(),
      panel.grid.minor.y = element_blank(),
      strip.background = element_rect(colour = "black", size = 0.5),
      legend.key       = element_blank()
    )
}

theme_minimal2 <- function(base_size = 12, base_family = "") {
  # Starts with theme_bw and then modify some parts
  theme_bw(base_size = base_size, base_family = base_family) %+replace%
    theme(
      legend.background = element_blank(),
      legend.key        = element_blank(),
      panel.background  = element_blank(),
      panel.border      = element_blank(),
      strip.background  = element_blank(),
      plot.background   = element_blank(),
      axis.ticks        = element_line(),
      axis.ticks.x     = element_blank(),
      axis.ticks.y     = element_blank(),
      axis.ticks.length = unit(0, "lines")
    )
}

[hadley]

@Katiedaisey would you be interested in doing a PR to make those changes? I'd really appreciate it.

[Katiedaisey]

@hadley Sure. Just let me check those are indeed the only conflicts and I'll send you one tomorrow.