r - ggplot2: dot plot with repeated measures and means -

that's first question in here, please, don't angry if anything..

the point is:

i have several timepoints (graft, day 0, day 60 etc...) , several samples each. samples have been measured , have several numbers each timepoint. i'd make dot plot placing dots according measured values (on y-axis) grouped timepoints (on x-axis). i'm totally new ggplot, i've succesfully created plot. examplary data.frame , code plot looks like:

data=data.frame(value=1:30, time=rep(c('d0', 'd1', 'd2'), each=10))  str(data) 'data.frame':   30 obs. of  2 variables: $ value: num  1 2 3 4 5 6 7 8 9 10 ... $ time : factor w/ 3 levels "d0","d1","d2": 1 1 1 1 1 1 1 1 1 1 ...  g=ggplot(data=data, aes(x=time, y=value)) g+geom_point() 

but have no idea how add short lines mark median values each timepoint... guess should use geom_segments somehow, don't know how deal x, xend, y , yend in case... advise me smth?

thank's all!

this sort of thing can use stat_summary geom of choice. example, add median point using long dash symbol , changing size looks ok.

ggplot(data = data, aes(x = time, y = value)) +      geom_point() +     stat_summary(fun.y = "median", geom = "point", pch = "_", size = 25) 

another alternative use crossbar or errorbar geom, have set ymin , ymax these. can set aesthetics ..y.. in order set them same y variable. changing width changes how long lines are.

ggplot(data = data, aes(x = time, y = value)) +      geom_point() +     stat_summary(fun.y = "median", geom = "crossbar",                 mapping = aes(ymin = ..y.., ymax = ..y..), width = .25)