Tue Mar  3 08:16:31 2020 

symdiff_test
  R version 3.4.4 (2018-03-15) 
  symdiff applies the symmetric finite difference formula to a function.

  symdiff(3*x-1, 4, 1 ) =  3 
  symdiff(3*x-1, 4, 1.0E-06 ) =  3 
  symdiff(sin, pi/4, 1 ) =  0.5950098 
  symdiff(sin, pi/4, 0.5 ) =  0.6780101 
  symdiff(sin, pi/4, 0.01 ) =  0.707095 
  symdiff(sin, pi/4 ) =  0.7071068 

symdiff_test
  Normal end of execution.
Tue Mar  3 08:16:31 2020