我有一张带有图例渐变的地图,我想为 NA 值添加一个框。我的问题非常类似于this one https://stackoverflow.com/questions/29151167/add-na-value-to-ggplot-legend-for-continuous-data-map and this one https://stackoverflow.com/questions/31705691/ggplot2-legend-for-na-in-scale-fill-brewer。我也读过这个话题 https://github.com/tidyverse/ggplot2/issues/410,但我在某处找不到“好的”解决方案,或者也许没有?
这是一个可重现的示例:
library(ggplot2)
map <- map_data("world")
map$value <- setNames(sample(-50:50, length(unique(map$region)), TRUE),
unique(map$region))[map$region]
map[map$region == "Russia", "value"] <- NA
ggplot() +
geom_polygon(data = map,
aes(long, lat, group = group, fill = value)) +
scale_fill_gradient2(low = "brown3", mid = "cornsilk1", high = "turquoise4",
limits = c(-50, 50),
na.value = "black")
所以我想为俄罗斯的 NA 值添加一个黑匣子。我知道,我可以用数字替换 NA,所以它会出现在渐变中,我想,我可以编写如下的解决方法,但所有这些解决方法对我来说似乎都不是一个很好的解决方案,而且我也想避免“毫无意义”的警告:
ggplot() +
geom_polygon(data = map,
aes(long, lat, group = group, fill = value)) +
scale_fill_gradient2(low = "brown3", mid = "cornsilk1", high = "turquoise4",
limits = c(-50, 50),
na.value = "black") +
geom_point(aes(x = -100, y = -50, size = "NA"), shape = NA, colour = "black") +
guides(size = guide_legend("NA", override.aes = list(shape = 15, size = 10)))
Warning messages:
1: Using size for a discrete variable is not advised.
2: Removed 1 rows containing missing values (geom_point).