Arima model

WN <- arima.sim(model = list(order = c(0, 0, 0)), n = 200)

A_function <- function(t){
  if (t < 101){
    return(0)
  }else if ((t > 100) & (t <201)){
    return(10*exp(-(t-100)/(20))*cos((2*pi*t)/(4)))
  }
}

B_function <- function(t){
  if (t < 101){
    return(0)
  }else if ((t > 100) & (t <201)){
    return(10*exp(-(t-100)/(200))*cos((2*pi*t)/(4)))
  }
}

C_function <- function(t){
  if ((t >= 101) & (t <= 200)){
    return(10*exp(-t/20)*cos((2*pi*t)/(4)))
  }else if ((t >= 1) & (t <= 100)){
    return(0)
  }
}

D_function <- function(t){
  if ((t >= 101) & (t <= 200)){
    return(10*exp(-t/200)*cos((2*pi*t)/(4)))
  }else if ((t >= 1) & (t <= 100)){
    return (0)
  }
}

result_A <- 1:200
result_B <- 1:200
result_C <- 1:200
result_D <- 1:200
for (i in 1:200){
  result_A[i] <- WN[i] + A_function(i)
  result_B[i] <- WN[i] + B_function(i)
  result_C[i] <- WN[i] + C_function(i)
  result_D[i] <- WN[i] + D_function(i)
}

par(mfrow = c(2,1))
plot.ts(result_A, xlab = 'Funcion de la pregun