How to make log10 ONLY first y-axis (not secondary y-axis) in ggplot in R-CodePudding

I would like to plot ONLY y-axis1 DATA (left axis, Var1, dotted line) as a log10 scale. The dotted line would therefore look higher on the y-axis and differences between 1 and 2 would be noticeable.

I have tried several things, but does not work ( I believe I am using them in the wrong order/place) such as:

coord_trans(y='log10')--> empty plot

scale_y_continuous(trans = log10_trans(),... --> makes both Var1 and Var 2 log10

scale_y_log10(breaks = trans_breaks("log10", function(x) 10^x),labels = trans_format("log10", math_format(10^.x)))--> makes both y axis log10 and removes y-axis2 (Var2)

data<- data.frame(
      Day=c(1,2,3,1,2,3,1,2,3),
      Name=rep(c(rep("a",3),rep("b",3),rep("c",3))),
      Var1=c(1090,484,64010,1090,484,64010,1090,484,64010),
      Var2= c(4,16,39,2,22,39,41,10,3))


ggplot(data)    
  geom_bar(aes(fill=Name, y=Var2*1000, x=Day),stat="identity", colour="black", position= position_stack(reverse = TRUE)) 
  geom_line(aes(x=Day, y=Var1),stat="identity",color="black", linetype="dotted", size=0.8) 
  geom_point(aes(Day, Var1), shape=8) 
  labs(title= "",
       x="",y=expression('Var1')) 
  scale_y_continuous(
    sec.axis=sec_axis(~./1000, name= expression(paste("Var2")))) 
  theme_classic() 
  scale_fill_grey(start = 1, end=0.1,name = "", labels = c("a", "b", "c"))

CodePudding user response：

I think the easiest way is to have the primary axis be the linear one, but put it on the right side of the plot. Then, you can have the secondary one be your log-transformed axis.

library(ggplot2)

data<- data.frame(
  Day=c(1,2,3,1,2,3,1,2,3),
  Name=rep(c(rep("a",3),rep("b",3),rep("c",3))),
  Var1=c(1090,484,64010,1090,484,64010,1090,484,64010),
  Var2= c(4,16,39,2,22,39,41,10,3))

# Max of secondary divided by max of primary
upper <- log10(3e6) / 80

breakfun <- function(x) {
  10^scales::extended_breaks()(log10(x))
}

ggplot(data)    
  geom_bar(aes(fill=Name, y=Var2, x=Day),
           stat="identity", colour="black", position= position_stack(reverse = TRUE)) 
  geom_line(aes(x=Day, y=log10(Var1) / upper),
            stat="identity",color="black", linetype="dotted", size=0.8) 
  geom_point(aes(Day, log10(Var1) / upper), shape=8) 
  labs(title= "",
       x="",y=expression('Var1')) 
  scale_y_continuous(
    position = "right",
    name = "Var2",
    sec.axis = sec_axis(~10^ (. * upper), name= expression(paste("Var1")),
                        breaks = breakfun)
  ) 
  theme_classic()  
  scale_fill_grey(start = 1, end=0.1,name = "", labels = c("a", "b", "c"))

^{Created on 2022-02-09 by the}

CodePudding user response：

You absolutely should read the answer @teunbrand linked to in the comment to your question. But for the matter of displaying log values on the left and original values on the right, you can use:

tibble(Day = 1:10,
       Val1 =10*Day) %>% 
    ggplot(aes(x = Day, y = log10(Val1)))  
    geom_col()  
    scale_y_log10(name = "log(Val1)",
                  sec.axis = sec_axis(~ 10^., name = "Val1"))