线性区域内的R-ggplot2外推回归线

我有以下数据框（附件）。我已经绘制了各种准直器/头组合的CR与A

(p <- ggplot(df,aes(x=A,y=CR,col=Head))+geom_point()+geom_line() +facet_grid(Collimator~Head, scales="fixed")+scale_x_continuous("Activity [MBq]", expand = c(0,0))+ylim(0,80000)+ ylab("Count Rate [cps]") + theme_bw()+theme(legend.position = "none"))

---

一种方法是制作一个新的数据框，该数据框只包含

准直器

和

头部

的前两个值。然后计算这两个值的斜率和截距值，并在

geom_abline（）

中使用它们绘制直线

 library(plyr)
#subset only firt two values
 df2<-ddply(df,.(Collimator,Head),function(x) head(x,2))
 head(df2)
   A0   T         A Counts    CR Head Collimator
1  76  97  63.45388  99780  3326   H1       HRGP
2 274  98 228.34282 317952 10598   H1       HRGP
3  76  85  64.88609 102830  3428   H2       HRGP
4 274  87 233.06284 328231 10941   H2       HRGP
5  76 328  41.29136 121230  4041   H1       LEGP
6 274 330 148.31347 424329 14144   H1       LEGP

#caclulate slope and intercept
 df3<-ddply(df2,.(Collimator,Head),summarise, int=coefficients(lm(CR~A))[1],
                      slop=coefficients(lm(CR~A))[2])
 df3
  Collimator Head      int      slop
1       HRGP   H1 527.5309  44.10241
2       HRGP   H2 529.3279  44.67324
3       LEGP   H1 143.0519  94.40105
4       LEGP   H2 146.2766  96.95737
5       LEHS   H1 567.3029 155.85205
6       LEHS   H2 694.4843 162.54077

ggplot(df,aes(x=A,y=CR,col=Head))+geom_point()+geom_line() + 
  facet_grid(Collimator~Head, scales="fixed") + 
  scale_x_continuous("Activity [MBq]", expand = c(0,0))+ ylim(0,80000) + 
  ylab("Count Rate [cps]") + 
  theme_bw()+theme(legend.position = "none")+
  geom_abline(data=df3,aes(intercept=int,slope=slop,color=Head))

库（plyr）
#仅子集前两个值
df2这应该可以做到：

library(ggplot2)
(p <- ggplot(df,aes(x=A,y=CR,col=Head))+
    geom_point()+geom_line() +
    facet_grid(Collimator~Head, scales="fixed")+
    scale_x_continuous("Activity [MBq]",
                       expand = c(0,0))+ylim(0,80000)+
  ylab("Count Rate [cps]") + theme_bw()+theme(legend.position = "none"))

 library(plyr)
 subdf <- ddply(df,c("Collimator","Head"),
                function(x) x[1:2,])
 p + geom_smooth(method="lm",data=subdf,colour="gray",se=FALSE,
                 fullrange=TRUE)

库（ggplot2）
（p
library(ggplot2)
(p <- ggplot(df,aes(x=A,y=CR,col=Head))+
    geom_point()+geom_line() +
    facet_grid(Collimator~Head, scales="fixed")+
    scale_x_continuous("Activity [MBq]",
                       expand = c(0,0))+ylim(0,80000)+
  ylab("Count Rate [cps]") + theme_bw()+theme(legend.position = "none"))

 library(plyr)
 subdf <- ddply(df,c("Collimator","Head"),
                function(x) x[1:2,])
 p + geom_smooth(method="lm",data=subdf,colour="gray",se=FALSE,
                 fullrange=TRUE)