rggplot2dataframeline-plot

How to draw a line plot in ggplot using a data.frame file?

Thank you for reading. I find that I am unable to draw line plot from my existing data as below:

a=structure(list(ID = structure(1:3, .Names = c("V2", "V3", "V4"
), .Label = c(" day1", " day2", " day3"), class = "factor"), 
    Protein1 = structure(c(3L, 1L, 2L), .Names = c("V2", 
    "V3", "V4"), .Label = c("-0.651129553", "-1.613977035", "-1.915631511"
    ), class = "factor"), Protein2 = structure(c(3L, 
    1L, 2L), .Names = c("V2", "V3", "V4"), .Label = c("-1.438858662", 
    "-2.16361761", "-2.427593862"), class = "factor")), .Names = c("ID", 
"Protein1", "Protein2"), row.names = c("V2", 
"V3", "V4"), class = "data.frame")

What I need is to draw a graph as below:

enter image description here

I have tried the following codes but the results are not ok;

qplot(ID, Protein1, data=a, colour=ID, geom="line")

Also:

a1<-melt(a, id.vars="ID")
ggplot(a1,aes(ID,value))+ geom_line()+geom_point()

So many thanks for your care.

Solution

  • First, you have to modify the structure of your data.frame : Protein1 & Protein2 should be numeric and not factors.

    a$Protein1 = as.numeric(as.character(a$Protein1))
a$Protein2 = as.numeric(as.character(a$Protein2))

    If you only want to plot "Protein1", you do not need to use melt first.

    ggplot(a, aes(x = ID, y = Protein1)) 
  + geom_point() 
  + geom_line(aes(group = 1)) 
  + ylim(-3,3)

    group = 1 permits connecting points with geom_line() : source

    Now, if you want to see Protein1 & Protein2 on the same plot, you can use melt :

    a1<-melt(a, id.vars="ID")
ggplot(a1, aes(x = ID, y = value, group = variable, color = variable)) 
  + geom_point() 
  + geom_line() 
  + ylim(-3,3)

    enter image description here