How to add conditional labelling for samples in ggplot

Question

I have this data frame called mydf. I am trying to plot this data as shown below, but I want to label only those samples that have more than 1.2 contamination (instead of everything). I also want to add a horizontal line at 1.2 contamination margin. How do I do this in R?

 mydf <- structure(list(sample.names = structure(c(2L, 3L, 4L, 5L, 6L, 
    1L, 7L, 8L, 9L, 10L), .Label = c("LPH-001-1", "LPH-001-10", "LPH-001-10_AK1", 
    "LPH-001-10_AK2", "LPH-001-10_PD", "LPH-001-10_SCC", "LPH-001-13", 
    "LPH-001-13_AK1", "LPH-001-13_AK2", "LPH-001-13_PD"), class = "factor"), 
        contamination = structure(c(5L, 1L, 4L, 2L, 2L, 4L, 3L, 8L, 
        7L, 6L), .Label = c("0.7", "1.0", "1.1", "1.2", "1.3", "1.4", 
        "1.7", "2.0"), class = "factor")), .Names = c("sample.names", 
    "contamination"), row.names = c(NA, -10L), class = "data.frame")

cc<- ggplot(mydf, aes(x=sample.names, y=contamination, label= mydf[,"sample.names"])) + geom_point()

        cc + geom_text()

Clean up the data before plotting, why numbers stored as factors? — zx8754
– zx8754, Commented Sep 6, 2016 at 8:04

Richard Telford · Accepted Answer · 2016-09-06 08:02:26Z

2

I would convert sample.names and contamination to character and numeric vectors respectively, then make a new vector of names that has placeholders for samples with contamination <= 1.2. geom_hline can add the horizontal line.

mydf$contamination <- as.numeric(as.character(mydf$contamination))
mydf$sample.names <- as.character(mydf$sample.names)
mydf$sample.names1.2 <- ifelse(mydf$contamination > 1.2, mydf$sample.names, "")

ggplot(mydf, aes(x=sample.names, y=contamination, label = sample.names1.2)) + 
  geom_point() +
  geom_text() +
  geom_hline(yintercept = 1.2)

answered Sep 6, 2016 at 8:02

Richard Telford

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