connecting points with lines in ggplot2 in r

Question

Here is my data:

    mydata <- data.frame (grp = c(  1,   1,   1,  1, 1,  1, 1, 1, 1, 
     2,2, 2, 2,2, 2, 2, 2, 2),
    grp1 = c("A", "A", "A", "A", "A",  "B", "B", "B", "B" ,  
    "A", "A", "A", "A",      "B", "B", "B", "B", "B"), 
   namef = c("M1", "M3", "M2", "M4", "M5","M1", "M3", "M4", 
    "M0", "M6", "M7", "M8",       "M10", "M6", "M7", "M8", "M9", "M10"),
     dgp = c(1, 1, 1, 1, 1,  1.15, 1.15,1.15, 1.15 ,
        2, 2, 2, 2,2.15, 2.15, 2.15, 2.15, 2.15), 
    position = c(1.1, 2.1, 3.2, 4.1, 5.0,
     1.1, 2.0, 5.0, 6.2, 1.0,3.0, 4.1, 5.0,  
    1.0, 2.1, 3.01, 4.0, 5.02))

require(ggplot2)

plt <- ggplot(mydata) +   geom_point(aes(position, dgp, 
group = factor(dgp)),   size = 2, colour = "purple") +
geom_text(data = mydata,aes(x=position,y=dgp + 0.05,
 label=namef))

plt

I want to connect point with same label from variable namef.

I thought geom_segment is appropriate to handle the situation:

require(grid)
plt + geom_segment(aes(xend = position, yend = dgp), 
arrow = arrow(length = unit(0.1,"cm")))

Answer 1

geom_line will connect points according to the group aesthetic, so:

ggplot(mydata, aes(position, dgp, group = namef)) +   
  geom_point(size = 2, colour = "purple") +
  geom_line() +
  geom_text(data = mydata,aes(x=position,y=dgp + 0.05, label=namef))

gets you this:

Also, it's generally better to put the aes() call in your original call to ggplot , and then only add an aes() or data argument to the individual geoms if you need to override some aesthetics.