in R I'm trying to interactively identify bin value in a histogram using the mouse. I think I need something equivalent to the identify() function for scatterplots. But identify() doesn't seem to work for histograms.
1 Answers
Use locator() to find the points, then lookup which interval the value sits in, make sure it is less than the y-value for the bar, then return the count:
set.seed(100)
h <- hist(rnorm(1:100))
# use locator() when doing this for real, i'm going to use a saved set of points
#l <- locator()
l <- list(x = c(-2.22, -1.82, -1.26, -0.79,-0.57, -0.25, 0.18, 0.75,
0.72, 1.26), y = c(1.46, 7.81, 3.79, 9.08, 17.11, 11.61, 15,
17.96, 5.9, 3.37))
# for debugging purposes - the nth value of the output should match where
# the n value is shown on the histogram
text(l, labels=1:10, cex=0.7, font=2)
fi <- findInterval(l$x, h$breaks)
sel <- (l$y > 0) & (l$y < h$counts[fi])
replace(h$counts[fi], !sel, NA)
#[1] 3 NA 9 14 NA 22 20 NA 13 7
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