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R function to draw figure labels in base plots
## from: https://logfc.wordpress.com/2017/03/15/adding-figure-labels-a-b-c-in-the-top-left-corner-of-the-plotting-region/
fig_label <- function(text, region="figure", pos="topleft", cex=NULL, ...) {
region <- match.arg(region, c("figure", "plot", "device"))
pos <- match.arg(pos, c("topleft", "top", "topright",
"left", "center", "right",
"bottomleft", "bottom", "bottomright"))
if(region %in% c("figure", "device")) {
ds <- dev.size("in")
# xy coordinates of device corners in user coordinates
x <- grconvertX(c(0, ds[1]), from="in", to="user")
y <- grconvertY(c(0, ds[2]), from="in", to="user")
# fragment of the device we use to plot
if(region == "figure") {
# account for the fragment of the device that
# the figure is using
fig <- par("fig")
dx <- (x[2] - x[1])
dy <- (y[2] - y[1])
x <- x[1] + dx * fig[1:2]
y <- y[1] + dy * fig[3:4]
}
}
# much simpler if in plotting region
if(region == "plot") {
u <- par("usr")
x <- u[1:2]
y <- u[3:4]
}
sw <- strwidth(text, cex=cex) * 60/100
sh <- strheight(text, cex=cex) * 60/100
x1 <- switch(pos,
topleft =x[1] + sw,
left =x[1] + sw,
bottomleft =x[1] + sw,
top =(x[1] + x[2])/2,
center =(x[1] + x[2])/2,
bottom =(x[1] + x[2])/2,
topright =x[2] - sw,
right =x[2] - sw,
bottomright =x[2] - sw)
y1 <- switch(pos,
topleft =y[2] - sh,
top =y[2] - sh,
topright =y[2] - sh,
left =(y[1] + y[2])/2,
center =(y[1] + y[2])/2,
right =(y[1] + y[2])/2,
bottomleft =y[1] + sh,
bottom =y[1] + sh,
bottomright =y[1] + sh)
old.par <- par(xpd=NA)
on.exit(par(old.par))
text(x1, y1, text, cex=cex, ...)
return(invisible(c(x,y)))
}
@BastienNguyen

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@BastienNguyen

BastienNguyen Jun 26, 2018

Very useful function but It seems that it did not work when using plot with log axis. Do you know how to place the text correctly when using log axis?

Very useful function but It seems that it did not work when using plot with log axis. Do you know how to place the text correctly when using log axis?

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