tests/testthat/test-demod.R

In swdft: Sliding Window Discrete Fourier Transform (SWDFT)

context("Complex and matching demodulation")

test_that("Complex demodulation matches SWDFT w/ moving average filter", {
  # --- Generate white-noise signal and corresponding SWDFT ---
  N <- 15
  window_size <- 5
  x <- rnorm(n=N, mean=0, sd=1)
  a <- swdft::swdft(x=x, n=window_size, type="fftw")$a * (1 / window_size)
  f0 <- sample(x=1:3, size=1) / window_size

  # --- Tests ---

  ## Verify that the shifted moving average filter matches the SWDFT after shifting
  x_demod_match <- swdft::complex_demod(x=x, f0=f0, smooth='ma', order=window_size, match_swdft=TRUE, window_size=window_size)
  expect_true(
    all( round(x_demod_match$demod$y_smooth[3:13], digits=5) == round(a[as.integer(f0 * window_size) + 1, 5:N], digits=5) )
  )

  ## Verify that we can shift the SWDFT to match the demodulation
  x_demod <- swdft::complex_demod(x=x, f0=f0, smooth='ma', order=window_size)
  k_swdft_demod <- swdft:::demod_swdft(a=a, k=round(f0 * window_size))
  expect_true(
    all.equal(target=round(k_swdft_demod$demod, digits=3), current=round(x_demod$demod$y_smooth,digits=3))
  )

  ## Other tests on class and length of outputs
  expect_true(all(class(x_demod_match) == c("swdft_demod", "swdft_mod")))
  expect_true(length(x_demod_match$coefficients$inst_amp) == length(x))
})

test_that("Matching demodulation works", {
  # --- Generate noiseless local cosine signal ---
  N <- 40
  n <- 16
  window_size <- 5
  x <- swdft::local_signal(N=N, A=1, Fr=2/n, phase=0, S=5, L=30)

  ## Run matching demodulation algorithm on the local periodic signal
  x_matching_demod <- swdft::matching_demod(x=x, n=n)

  ## Run various tests on the outptu
  expect_true(all(abs(x_matching_demod$residuals) < 1))
  expect_true(all(class(x_matching_demod) == c("swdft_matching_demod", "swdft_demod", "swdft_mod")))
})