facet_grid背对背直方图失败 [英] facet_grid of back to back histogram failing

问题描述

I am having some trouble creating a facet grid of a back-to-back histogram created with ggplot.

# create data frame with latency values
latc_sorted <- data.frame(  
subject=c(1,1,1,1,1,2,2,2,2,2),
grp=c("K_N","K_I","K_N","K_I","K_N","K_I","K_N","K_I","K_N","K_I"), 
lat=c(22,45,18,55,94,11,67,22,64,44)    
)   

# subset and order data 
x.sub_ki<-subset(latc_sorted, grp=="K_I")
x.sub_kn<-subset(latc_sorted, grp=="K_N")
x.sub_k<-rbind(x.sub_ki,x.sub_kn)
x=x.sub_ki$lat
y=x.sub_kn$lat
nm<-list("x","y")

# make absolute values on x axis
my.abs<-function(x){abs(x)}

# plot back-to-back histogram
hist_K<-qplot(x, geom="histogram", fill="inverted", binwidth=20) +
geom_histogram(data=data.frame(x=y), aes(fill="non-inverted", y=-..count..),
binwidth= 20) + scale_y_continuous(formatter='my.abs') + coord_flip() + 
scale_fill_hue("variable")

hist_K

这种情况很好，但如果我尝试以下我得到错误：
错误：铸造公式包含未在熔融数据中找到的变量：x.sub_k $ subject

this plots fine but if I try the following I get the error: Error: Casting formula contains variables not found in molten data: x.sub_k$subject

hist_K_sub<-qplot(x, geom="histogram", fill="inverted", binwidth=20) +
geom_histogram(data=data.frame(x=y), aes(fill="non-inverted", y=-..count..),
binwidth= 20) + scale_y_continuous(formatter='my.abs') + coord_flip() + 
scale_fill_hue("variable")+
facet_grid(x.sub_k$subject ~ .)

hist_K_sub

任何想法是什么导致这个失败？

any ideas what is causing this to fail?

推荐答案

问题在于 facet_grid 在传递给各层的data.frames中查找。您已创建（隐式和显式）仅具有 lat 数据并且没有主题信息的data.frames 。如果您使用 x.sub_ki 和 x.sub_kn ，它们确实具有主题与 lat 值关联的变量。

The problem is that the variables referenced in facet_grid are looked for in the data.frames that are passed to the various layers. You have created (implicitly and explicitly) data.frames which have only the lat data and do not have the subject information. If you use x.sub_ki and x.sub_kn instead, they do have the subject variable associated with the lat values.

hist_K_sub <- 
ggplot() +
  geom_histogram(data=x.sub_ki, aes(x=lat, fill="inverted",     y= ..count..), binwidth=20) +
  geom_histogram(data=x.sub_kn, aes(x=lat, fill="not inverted", y=-..count..), binwidth=20) +
  facet_grid(subject ~ .) +
  scale_y_continuous(formatter="my.abs") +
  scale_fill_hue("variable") +
  coord_flip()

hist_K_sub

我也从qplot转换为完整的ggplot语法;这表明ki和kn的平行结构更好。

I also converted from qplot to full ggplot syntax; that shows the parallel structure of ki and kn better.

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