z<-outer(x1,x2,fr2)
Error in FUN(X, Y, ...) : unused argument (Y)
>  
>  image(x1,x2,z)
Error in image.default(x1, x2, z) : object 'z' not found
>  contour(x1,x2,z,add=T)
Error in contour.default(x1, x2, z, add = T) : object 'z' not found
>  persp(x1,x2,z)
Error in persp.default(x1, x2, z) : object 'z' not found
>  persp(x1,x2,z,box=T,border = T,theta = 45,phi = 35)
Error in persp.default(x1, x2, z, box = T, border = T, theta = 45, phi = 35) :
  object 'z' not found
>  optim(c(-5,5),fr2,grr)    这是编译提示