Having different symbols for datapoints using ggplot() in R

Question

I'm very new to R and I hope this question is still interesting enough. I have the following dataframe:

> dput(df)
structure(list(Proportion = c(0.491475825983558, 0.624947117938639, 
0.284285973983444, 0.459936074937072, 0.438167575182789, 0.5923527, 
0.269347638359089, 0.444195335296524, 0.472343382529259, 0.6119936, 
0.280545311041942, 0.45582336843016), Lower = c(0.373501802431026, 
0.506815311121949, 0.196793171052086, 0.344394223066228, 0.342020291619279, 
0.4962054, 0.197239652248339, 0.347543569904938, 0.362690139261045, 
0.5158463, 0.198654362934906, 0.347479674558168), Upper = c(0.610508712286318, 
0.729864865043791, 0.39179224043653, 0.580031198686217, 0.539194328764963, 
0.6885, 0.356122647401151, 0.545263076314964, 0.5847316572176, 
0.7081409, 0.380178492952045, 0.56851602179505), Area = c("SNP", 
"SNP", "LGCA", "LGCA", "SNP", "SNP", "LGCA", "LGCA", "SNP", "SNP", 
"LGCA", "LGCA"), Time = c("Day", "Night", "Day", "Night", "Day", 
"Night", "Day", "Night", "Day", "Night", "Day", "Night"), Collar = c(41361, 
41361, 41361, 41361, 41365, 41365, 41365, 41365, 41366, 41366, 
41366, 41366)), row.names = c(NA, -12L), class = c("tbl_df", 
"tbl", "data.frame"))

For which I have created the following plot:

Using the script below:

dfnew <- df %>% 
  mutate(ymin = Proportion - Lower,
         ymax = Proportion + Upper)

p <- ggplot(data = dfnew, aes(x = Time, y = Proportion, color=Area, group=Area)) +
  geom_point(size = 6, stroke = 0, shape = 16, 
             position = position_dodge(width = 0.1))+
  geom_errorbar(aes(ymin = Lower, ymax = Upper), width=0.1, size=1,
                position = position_dodge(width = 0.1)) + 
  theme(axis.text=element_text(size=15),
        axis.title=element_text(size=20)) +
  scale_color_manual(values = c("SNP" = "coral", 
                                "LGCA" = "darkgoldenrod2")) +
  geom_line(size=1,linetype="dotted")
p

I would like plot different symbols (e.g. ∆, O, ◊) accounting for the different collars in df. Also, I would like these to be moved slightly (position_dodge) so that not all points are on top of each other.

How can I access a symbol library and implement it into my script?

Any help would be very appreciated!

Answer 1

If you map the shape within an aes() call you can vary the shapes and if you want specific shapes you can use scale_shape_manual() for example just like with the colors. The dodging within one group can be achieved by either using geom_jitter() or replacing position_dodge() with position_jitterdodge(). Unfortunately this messes with the errorbars.

EDIT: There is a fix for the error bars in this answer by Marcelo. I also included a way to connect the same symbols with the dotted line. This is easiest done by adding another grouping column to your data.

dfnew <- df %>% 
  mutate(ymin = Proportion - Lower,
         ymax = Proportion + Upper,
         linegroup = paste(Area, Collar))

set.seed(2)
myjit <- ggproto("fixJitter", PositionDodge,
                 width = 0.6,
                 dodge.width = 0,
                 jit = NULL,
                 compute_panel =  function (self, data, params, scales) 
                 {

                   #Generate Jitter if not yet
                   if(is.null(self$jit) ) {
                     self$jit <-jitter(rep(0, nrow(data)), amount=self$dodge.width)
                   }

                   data <- ggproto_parent(PositionDodge, self)$compute_panel(data, params, scales)

                   data$x <- data$x + self$jit
                   #For proper error extensions
                   if("xmin" %in% colnames(data)) data$xmin <- data$xmin + self$jit
                   if("xmax" %in% colnames(data)) data$xmax <- data$xmax + self$jit
                   data
                 } )


ggplot(data = dfnew, aes(x = Time, y = Proportion, color=Area, group=linegroup)) +
  geom_point(aes(shape = as.character(Collar)), size = 6, stroke = 0, 
             position = myjit)+
  geom_line(aes(group = linegroup),linetype = "dotted",size=1, position = myjit) +
  theme(axis.text=element_text(size=15),
        axis.title=element_text(size=20)) +
  geom_errorbar(aes(ymin = Lower, ymax = Upper), width=0.3, size=1,
                position = myjit) +
  scale_color_manual(values = c("SNP" = "coral", 
                                "LGCA" = "darkgoldenrod2"))