Вы можете напрямую манипулировать объектом гистограммы:
histo <- hist(df8$difference)
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histo$counts[1:4] <- -histo$counts[1:4]
plot(histo)
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Воспроизводимые данные:
df8 <- structure(list(difference = c(-2, 6, 7, -8, 6, 5, 2, 4, -3, 1,
9, 3, -4, 2, 6, -1, 11, 5, 2, 8, 15, 0, 9, -5, 1, 16, 12, 14,
-7, -11, -8, 1, 1, 11, 6, 3, 2, -2, 8, -5, NA, -5, 2, 10, 7,
1, 9, -5, 7, 4, 5, 9, NA, 13, -1, 2, 5, 6, 9, 4, 0, 3, -4, 3,
2, 4, 14, -9, 12, 6, 0, 6, 6, -5, -1, -6, 11, 2, 3, 3, 5, 1,
-5, 6, 19, 15, -4, 9, -1, -4, -4, -10, NA, NA, NA, 0, 0, 15,
7, -10, 2, 0, -5, -5, 10, -2, -8, 18, 1, -1, 7, -5, -9, -6, -18,
11, -1, NA, 11, -4, 7, 5, 20, 3, 2, 0, 2, 2, 11, -2, -5, 0, 6,
-2, 6, -2, -5, -1, -5, -6, 3, -1, -9, -1, 9, NA, -6, 4, -5, 8,
0, -2, 1, 9, 3, 9, -3, 2, 8, 0, 2, -4, 6, 4, -5)),
class = "data.frame", row.names = c(NA, -165L))
Создано в 2020-02-21 пакетом представ. (v0.3.0)