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How to make geom_text () parallel to geom_segment () on log-lin scale?

You need to annotate the line on the chart. How to make a text string (here "0000000000") parallel to the string that it annotates?

require(ggplot2)
require(scales)
x=c(1:10)
y=2^x
data_line <- data.frame(x=3,xend=8,y=2^8,yend=2^9)
line <- geom_segment(data=data_line,aes(x=x,xend=xend,y=y,yend=yend),color="blue")
angle= atan((data_line$yend - data_line$y) / (data_line$xend - data_line$x))*(180/pi)
text <- annotate("text",x=data_line$x,y=data_line$y,label="0000000000",angle=angle)
qplot(x=x,y=y,geom="line") + line + text + scale_y_log10()
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2 answers

The solution is as follows

require(ggplot2)
require(scales)
coord_ratio = ((1+sqrt(5))/2)^-1
data <- data.frame(x=c(1:10),y=10^(1:10))
line_coord <- data.frame(x=round(runif(5,1,5)),
                     y=round(runif(5,10^1,10^5)),
                     xend=round(runif(5,5,10)),
                     yend=round(runif(5,10^5,10^10)))
line_draw <- geom_segment(data=line_coord,aes(x=x,y=y,xend=xend,yend=yend),color="blue")
angle = atan((log10(line_coord$yend)*(coord_ratio)-log10(line_coord$y)*coord_ratio) / (line_coord$xend-line_coord$x))*(180/pi)
text <- annotate("text",x=line_coord$x,y=line_coord$y,label="LLLLLLLLLL",angle=angle,hjust=-0.1,vjust=-0.5)
qplot(data$x,data$y) + scale_y_log10() + coord_fixed(ratio=coord_ratio) + line_draw + text

result: i.imgur.com/0JBGAiO.png

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Here is one way to do this with coord_fixed:

ratio <- .25/(256/5) # 256/5 is from (512-256)/(8-3)
df1 <- data.frame(x = 1:10, y = 2^(1:10))
d <- data.frame(xmin=3, xmax=8, ymin=256, ymax=512, annotation="bla")
ggplot() + geom_line(data = df1, aes(x=x, y=y)) + 
    geom_segment(data=d, aes(x=xmin, xend=xmax, y=ymin, yend=ymax)) + 
    geom_text(data = d, aes(x=4, y=256/5 * 4 + 512/5, 
    label=annotation, angle=atan2((ymax-ymin)*ratio, 
    (xmax-xmin)) * 180/pi), vjust=-0.5) + coord_fixed(ratio=ratio)

enter image description here

To get the scale of the log, it looks a bit more complicated:

ratio <- -log10(.25/(256/5)) # 256/5 is from (512-256)/(8-3)
df1 <- data.frame(x = 1:10, y = 2^(1:10))
d <- data.frame(xmin=3, xmax=8, ymin=256, ymax=512, annotation="bla")
ggplot() + geom_line(data = df1, aes(x=x, y=y)) + 
    geom_segment(data=d, aes(x=xmin, xend=xmax, y=ymin, yend=ymax)) + 
    geom_text(data = d, aes(x=4, y=256/5 * 4 + 512/5, 
    label=annotation, angle=log10(atan2((ymax-ymin)*ratio, 
    (xmax-xmin)) * 180/pi)), vjust=-0.5) + coord_fixed(ratio=ratio) + scale_y_log10()

enter image description here

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