r - Hist中Gamma分布的拟合曲线

Question

当我运行这个时:

x<-c(73,6,77,81,91,120,150,61,65,68,18,20,23,12,14,18,23,26,26,27,2,3,3,40,41,41,6,10,11,12,37,38,38,6,73,6,51)
a<-1.286486;b<-30.59584

hist(x,breaks=c(0,20,40,60,80,100,120,160),probability = T,xaxt="n")
curve(dgamma(x,a,b),from=0,to=160,col="red",lwd=2,add=T)

它应该在直方图上生成 Gamma 分布曲线。相反，它只是沿着 x 轴绘制一条平坦的线。

我在这里做错了什么？

Answer 1

您的模型系数不正确。速率参数应接近 0.03。

x<-c(73,6,77,81,91,120,150,61,65,68,18,20,23,12,14,18,23,26,26,27, 2,3,3,40,41,41,6,10,11,12,37,38,38,6,73,6,51)

library(fitdistrplus)
model<-fitdist(x, "gamma")
print(model$estimate)
#    shape      rate 
#1.1911710 0.0311047 
a=model$estimate[1]
b=model$estimate[2]    

h<-hist(x,breaks=c(0,20,40,60,80,100,120,160),probability = T)
curve(dgamma(x,a,b),from=0,to=160,col="red",lwd=2,add=T)