CODEWITHSUNDEEP
rggplot2line
SC2
SC2

Reputation: 323

R ggplot2 draw line from point to y=0

I have a data frame with 3 columns. I am plotting a factor (X) by a numeric variable (Prob). I would like to draw a line from each point down to the y=0 line. I tried to do this with the code below after reading this post R ggplot vertical and horizontal line intercept at center. The results were not what I expected. I think this may have to do with the fact that my x-axis variable is a factor. Is there a better way that I can do this?

    pmf.data = as.data.frame(c(0,1,2,"NA"))
    pmf.data$Prob = c(0.4921875, 0.015625, 0.4921875, 0)
    colnames(pmf.data)[1] = c("X")
    pmf.data$label = c("P0", "P1", "P2", "PNA")

    ggplot(data=pmf.data, aes(x=X, y=Prob)) + geom_point() +
      geom_text(aes(label = label), hjust = 2) +
      geom_segment(aes(xend=Prob, yend=0), color="blue") +
      ylab(expression(bold(paste(f[(X)](x))))) +
      ggtitle("Multinomial pdf for X")

Upvotes: 1

Views: 4777

Answers (1)

Didzis Elferts
Didzis Elferts

Reputation: 98599

If you need a vertical line that goes to y=0 then xend= values inside the geom_segment() should be the same as x value - that is - X.

ggplot(data=pmf.data, aes(x=X, y=Prob)) + geom_point() +
  geom_text(aes(label = label), hjust = 2) +
  geom_segment(aes(xend=X, yend=0), color="blue") +
  ylab(expression(bold(paste(f[(X)](x))))) +
  ggtitle("Multinomial pdf for X")

The same effect as with geom_segment() can be atchieved with geom_bar() and setting width= some low value.

ggplot(data=pmf.data, aes(x=X, y=Prob))+geom_bar(stat="identity",width=0.01)

Upvotes: 3

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