I would like to estimate the seasonal component in the series a below using harmonic regression. I am new to harmonic regression so would appreciate someone showing me how it works and how it is done in R.
a<-c(9007,8106,8928,9137,10017,10826,11317,10744,9713,9938,9161,8927,7750,6981,8038,8422,8714,9512,10120,
9823,8743,9129,8710,8680,8162,7306,8124,7870,9387,9556,10093,9620,8285,8433,8160,8034,7717,7461,7776,
7925,8634,8945,10078,9179,8037,8488,7874,8647,7792,6957,7726,8106,8890,9299,10625,9302,8314,8850,8265,
8796,7836,6892,7791,8129,9115,9434,10484,9827,9110,9070,8633,9240)
plot(a,type="b")
