我手上有两组数据，想用y=ax^b来拟合，在使用R运行的时候，一直报错。求大佬们指点一下，怎么改代码才能算出估计值a 、b

x<-c(2000,2001,2002,2003,2004,2005,2006,2007,2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019)
y<-c(8.6,8.9,9.5,11,15.2,20,26.2,33.27,43.41,62.06,101.72,131.15,170.73,127.67,161.55,271.36,287.47,301.04,378.97,411.75)
cor(x,y)
test=nls(y~a*x^b,start=(list(a=1,b=1)))