When I run this:
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)
It should generate the curve of the Gamma Distribution on the histogram. Instead, it just makes a flat line along the x-axis.
What am I doing wrong here?
Your coefficients to the model are incorrect. The rate parameter should be closer to 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)
It appears that your x vector doesn't contain the realizations of gamma distribution with those parameters (a,b). Try this:
a<-1.286486
b<-30.59584
num<-rgamma(1000,a,b)
hist(num,nclass = 100,freq=F)
curve(dgamma(x,a,b),col="red",lwd=2,add=T)