My example is:
qplot(mtcars$mpg) + annotate(geom = "text", x = 30, y = 3, label = "Some text\nSome more text")
How do I get the text here to be left aligned? So that the 'Some's line up with each other.
hjust = 0 does what you want. hjust stands for horizontal justification, 0 will be left-justified, 0.5 will be centered, and 1 will be right-justified.
qplot(mtcars$mpg) +
annotate(geom = "text", x = 30, y = 3,
label = "Some text\nSome more text",
hjust = 0)
See also vjust for vertical justification.
In ggplot2, these arguments are present any time text preferences are set. They work for annotate, geom_text, or in element_text when adjusting theme options.
If you look at ?geom_text, you can find text string options: "left", "middle", or "right", (for hjust), "top", "center", "bottom" for vjust, and for either "inward" and "outward" which will always adjust in toward or out away from the center.
This behavior is similar in many base graphics functions, such as the adj argument for par, used by text(), mtext(), and title(), which can be vector of length 2 for the horizontal and vertical justificatons. Also the hadj and padj arguments to axis() for justifications horizontal to and perpendicular to the axis.
来源：https://stackoverflow.com/questions/26684023/how-to-left-align-text-in-annotate-from-ggplot2