Drawing ggplot with different line colour and point shapes-CodePudding

I tried to draw a ggplot with below data and aesthetics

  library(ggplot2)
  mydata = rbind(data.frame('date' = as.Date(c('2010-01-01', '2011-01-01', '2012-01-01')), var1 = c('A', 'A', 'A'), var2 = c('X', 'X', 'X'), val = c(10, 3, 10)),
            data.frame('date' = as.Date(c('2010-01-01', '2011-01-01', '2012-01-01')), var1 = c('B', 'B', 'B'), var2 = c('X', 'X', 'X'), val = c(10 2, 3 2, 10 2)),
            data.frame('date' = as.Date(c('2010-01-01', '2011-01-01', '2012-01-01')), var1 = c('A', 'A', 'A'), var2 = c('Y', 'Y', 'Y'), val = c(10-2, 3-2, 10-2)),
            data.frame('date' = as.Date(c('2010-01-01', '2011-01-01', '2012-01-01')), var1 = c('B', 'B', 'B'), var2 = c('Y', 'Y', 'Y'), val = c(10 5, 3 5, 10 5)))

ggplot(data = mydata, aes(x = date))  
    geom_line(aes(y = val, color = var1))  
    geom_point(aes(y = val, color = var1, shape = var2))

This approach is generating a strange plot. I wanted to draw 4 different lines on same date in x-axis, where var1 to be distinguished by colour and var2 to be distinguished by point shape.

Is there any way to achieve this?

CodePudding user response：

You need to give geom_line some way to tell which points to connect. color = var1 is all it has, so it is connecting all points with the same var1 values. You want a separate line for each group defined by var1 AND var2, so we combine those and give it to the group aesthetic:

ggplot(data = mydata, aes(x = date))  
    geom_line(aes(y = val, color = var1, group = paste(var1, var2)))  
    geom_point(aes(y = val, color = var1, shape = var2))   
    guides(color = guide_legend(override.aes = list(shape = NA)))

CodePudding user response：

You can move your point and line aesthetic mappings to the global mapping:

ggplot(data = mydata, aes(x = date, y=val, color=var1, shape=var2))  
  geom_line()  
  geom_point()   
  # as shown by @Gregor Thomas solution below
  guides(color = guide_legend(override.aes = list(shape = NA)))