如何在同一图表中绘制R中ggplot2的两组数据的直方图和频率多边形

Question

我有两组数据,我希望得到一个包含每组数据的直方图和频率多边形的图表.

我的数据框df如下:

'data.frame':   20000 obs. of  2 variables:
 $ measure   : num  -0.566 0.321 0.125 1.353 -1.288 ...
 $ processing: Factor w/ 2 levels "before","after": 1 1 1 1 1 1 1 1 1 1 ...

     measure processing
1 -0.5656801     before
2  0.3210458     before
3  0.1252706     before
4  1.3532248     before
5 -1.2877305     before
6  0.3225545     before

我的代码如下:

png("figure_%d.png")
set.seed(2014)
n <- 10000
before <- rnorm(n)
df_1 <- data.frame(measure=before)
df_1$processing <- factor("before")

after <- before-rnorm(n,mean=1,sd=0.1)
df_2 <- data.frame(measure=after)
df_2$processing <- factor("after")

df<-rbind(df_1,df_2)

library(ggplot2)


print(ggplot(df, aes(measure,colour=processing))+geom_freqpoly())

print(ggplot(df, aes(measure,fill=processing))+geom_density(alpha=0.5))

print(ggplot(df_1, aes(measure,fill=processing))+geom_histogram(alpha=0.5))
print(ggplot(df_2, aes(measure,fill=processing))+geom_histogram(alpha=0.5))
print(ggplot(df, aes(measure,fill=processing))+geom_histogram(alpha=0.5))

print(ggplot(df, aes(measure,fill=processing,colour=processing))+geom_freqpoly()+geom_histogram(alpha=0.5))

现在,之后

ggplot(df, aes(measure,colour=processing))+geom_freqpoly()

我得到下图

其中两个频率多边形是预期的.

后

ggplot(df, aes(measure,fill=processing))+geom_density(alpha=0.5)

我得到下图

并且两个密度重叠的地方我得到了预期的"混合"颜色.

现在我想得到一个带有两个直方图的数字; 首先,我在两个单独的图中绘制两个直方图:使用代码

ggplot(df_1, aes(measure,fill=processing))+geom_histogram(alpha=0.5)

我得到下图

和代码

ggplot(df_2, aes(measure,fill=processing))+geom_histogram(alpha=0.5)

我得到下图

这两个直方图都是预期的.

当我尝试使用此代码在同一图表中绘制直方图时,问题就出现了

ggplot(df, aes(measure,fill=processing))+geom_histogram(alpha=0.5)

我得到这个数字

我无法解释为什么绿色直方图高于红色直方图.此外,在两个直方图"重叠"的情况下,我没有得到"混合"颜色.

尝试添加频率多边形会使问题恶化,使用此代码

ggplot(df, aes(measure,fill=processing,colour=processing))+geom_freqpoly()+geom_histogram(alpha=0.5)

我得到这个数字

频率多边形在我看来是正确的,但直方图是错误的,如上图所示.

我究竟做错了什么？

输出version是

platform       x86_64-pc-linux-gnu         
arch           x86_64                      
os             linux-gnu                   
system         x86_64, linux-gnu           
status                                     
major          3                           
minor          0.2                         
year           2013                        
month          09                          
day            25                          
svn rev        63987                       
language       R                           
version.string R version 3.0.2 (2013-09-25)
nickname       Frisbee Sailing 

输出sessionInfo()是

R version 3.0.2 (2013-09-25)
Platform: x86_64-pc-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] methods   stats     graphics  grDevices utils     datasets  base     

other attached packages:
[1] ggplot2_0.9.3.1

loaded via a namespace (and not attached):
 [1] colorspace_1.2-4   dichromat_2.0-0    digest_0.6.4       grid_3.0.2        
 [5] gtable_0.1.2       labeling_0.2       MASS_7.3-29        munsell_0.4.2     
 [9] plyr_1.8           proto_0.3-10       RColorBrewer_1.0-5 reshape2_1.2.2    
[13] scales_0.2.3       stringr_0.6.2 

Answer 1

geom_histogram与参数一起使用position = "identity".positionis 的默认值"stack".在这种情况下,条不重叠但是堆叠.

geom_histogram(alpha = 0.5, position = "identity")

完整的代码:

library(ggplot2)
ggplot(df, aes(measure, fill = processing)) + 
  geom_histogram(alpha = 0.5, position = "identity")