R 基于大小向ggplot2 geom_平铺图添加图例

我正在使用

geom_tile

在ggplot2中创建波动图，并希望为大小添加图例。我不知道该怎么做。这里是一个MWE：

library(dplyr)
library(ggplot2)

# create data frame of total number of passengers in each Sex-Age group

df <- data.frame(Titanic) %>% group_by(Sex, Age) %>%
    summarise (freq = sum(Freq))

# calculate the lengths of the sides of the tiles so the largest has
# area = 1 and the others are smaller proportional to frequency

df$tileside <- sqrt(df$freq / max(df$freq))

df

## Source: local data frame [4 x 4]
## Groups: Sex [?]
## 
##      Sex    Age  freq  tileside
##   (fctr) (fctr) (dbl)     (dbl)
## 1   Male  Child    64 0.1959396
## 2   Male  Adult  1667 1.0000000
## 3 Female  Child    45 0.1643003
## 4 Female  Adult   425 0.5049248
# using geom_tile, no size legend

ggplot(df, aes(x = Sex, y = Age, 
               height = tileside, width = tileside)) +
    geom_tile() + coord_fixed (ratio = 1)

问题是这些方块太小，如果我用scale_size（）重新缩放它们，我就失去了fluctation图最重要的特征——方块的面积与频率成正比。（即使不重新缩放，我也不确定是否满足此条件——很难说面积是如何计算的）

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非常感谢您的帮助。

关于尺寸问题，您可以使用

缩放尺寸面积
。我还加了颜色

ggplot(df, aes(x = Sex, y = Age, size = freq, color = freq)) +
  geom_point(shape = 15)  + coord_fixed (ratio = 1) + 
  scale_size_area(max_size = 20) +
  scale_color_gradient(high="red", low="black", guide = "legend") 


ggplot(df, aes(x = Sex, y = Age, size = freq, color = freq)) +
  geom_point(shape = 15)  + coord_fixed (ratio = 1) + 
  scale_size_area(max_size = 20) +
  scale_color_gradient(high="red", low="black", guide = "legend")