为stat_density2d绘图手动设置scale_alpha

Question

我想绘制本地建筑的月度地图，具体使用ggplot2中的stat_density2d。我使用下面的代码：

library(ggmap) 
options(stringsAsFactors=T) 

mar_2016 <- structure(list(Latitude = c(47.6064785, 47.6086266, 47.61556306, 
             47.5335102, 47.53424442, 47.62629031, 47.66231885, 47.55882248, 
             47.63847192, 47.63847192, 47.63847192, 47.63846822, 47.66045328, 
             47.64787497, 47.6774562, 47.61126358, 47.61126358, 47.62041964, 
             47.56586818, 47.56600353), Longitude = c(-122.3313647, -122.32373921, 
                       -122.33276181, -122.3473748, -122.29267751, -122.32268625, -122.28147251, 
                       -122.36343703, -122.36995433, -122.36995433, -122.36995433, -122.36979987, 
                       -122.30463329, -122.37841989, -122.31846715, -122.31515559, -122.31515559, 
                       -122.35567747, -122.3694264, -122.36942834)), .Names = c("Latitude", 
                                      "Longitude"), row.names = c(NA, -20L), class = "data.frame") 

apr_2016 <- structure(list(Latitude = c(47.62373953, 47.61304116, 47.57543057, 
             47.59216, 47.66411106, 47.71560842, 47.55499461, 47.55878986, 
             47.5224678, 47.5224678, 47.63419063, 47.70380892, 47.6309837, 
             47.60766995, 47.52517771, 47.68700879, 47.68495153, 47.6733502, 
             47.61578904, 47.66961751, 47.62981265, 47.62126347, 47.60219778, 
             47.6086266, 47.52835462, 47.67514813, 47.67514813, 47.66513236, 
             47.56720557, 47.66590858), Longitude = c(-122.30442288, -122.34060091, 
                       -122.39628552, -122.29016643, -122.34337082, -122.31338271, -122.38583914, 
                       -122.26472731, -122.35949442, -122.35949442, -122.35408737, -122.37250127, 
                       -122.3076156, -122.32802388, -122.36489489, -122.38298825, -122.36237138, 
                       -122.35121936, -122.33727143, -122.36591715, -122.29125798, -122.32173169, 
                       -122.33348074, -122.32373921, -122.39195911, -122.28949534, -122.28949534, 
                       -122.28937395, -122.39185006, -122.2962011)), .Names = c("Latitude", 
                                      "Longitude"), row.names = c(412L, 416L, 417L, 426L, 427L, 428L, 
                                             429L, 434L, 437L, 438L, 454L, 456L, 475L, 489L, 490L, 491L, 492L, 
                                             493L, 494L, 495L, 496L, 507L, 510L, 516L, 525L, 526L, 527L, 528L, 
                                             529L, 541L), class = "data.frame") 


denny_park = get_map(location=c(-122.3437739, 47.6193031), zoom=15) 
ggmap(denny_park) + 
    geom_density2d(data = apr_2016, aes(x = Longitude, y = Latitude), size = 0.3) + 
    stat_density2d(data = apr_2016, 
       aes(x = Longitude, y = Latitude, fill = ..level.., alpha = ..level..), size = 0.01, 
       bins = 16, geom = "polygon") + scale_fill_gradient(low = "green", high = "red") + 
    scale_alpha(range = c(0, 0.3), guide = FALSE) + 
    ggtitle("April 2016") 

ggmap(denny_park) + 
    geom_density2d(data = mar_2016, aes(x = Longitude, y = Latitude), size = 0.3) + 
    stat_density2d(data = mar_2016, 
       aes(x = Longitude, y = Latitude, fill = ..level.., alpha = ..level..), size = 0.01, 
       bins = 16, geom = "polygon") + scale_fill_gradient(low = "green", high = "red") + 
    scale_alpha(range = c(0, 0.3), guide = FALSE) + 
    ggtitle("March 2016") 

产生和

我如何可以手动设置stat_density()填充参数为这两个地块同一个传奇？根据此question，..level..参数通过调用MASS::kde2d来计算。手动调用此给出一个列表：

R> apr_2016_kde <- MASS::kde2d(apr_2016$Longitude, apr_2016$Latitude) 
R> str(apr_2016_kde) 
List of 3 
$ x: num [1:25] -122 -122 -122 -122 -122 ... 
$ y: num [1:25] 47.5 47.5 47.5 47.5 47.6 ... 
$ z: num [1:25, 1:25] 23.2 27 30.2 32.7 34.2 ... 

这question是非常接近的，但抱怨错误：未知参数：减免stat_density2d()在GGPLOT2版本2.1.0

Answer 1

相同limits参数添加到scale_fill_gradient两个地块。例如，scale_fill_gradient(low = "green", high = "red", limits=c(0,70000))（或您希望的任何范围）。然后相同的颜色将被映射到每个图中相同的值。

这里的情节是什么样子与我加了限制：

（注：你的问题的标题提到scale_alpha，但你的问题的身体询问如何获得相同的填充传奇。我假设你想在每个情节中使用相同的填充图例，但请让我知道你是否想要不同的东西。）