Band-pass signals

Usage

band_pass1(x, sample_rate, lb, ub, domain = 1, ...)

band_pass2(
  x,
  sample_rate,
  lb,
  ub,
  order,
  method = c("fir", "butter"),
  direction = c("both", "forward", "backward"),
  window = "hamming",
  ...
)

Arguments

x: input signals, numeric vector or matrix. x must be row-major if input is a matrix: each row is a channel, and each column is a time-point.
sample_rate: sampling frequency
lb: lower frequency bound of the band-passing filter, must be positive
ub: upper frequency bound of the band-passing filter, must be greater than the lower bound and smaller than the half of sampling frequency
domain: 1 if x is in time-domain, or 0 if x is in frequency domain
...: ignored
order: the order of the filter, must be positive integer and be less than one-third of the sample rate
method: filter type, choices are 'fir' and 'butter'
direction: filter direction, choices are 'forward', 'backward', and 'both' directions
window: window type, can be a character, a function, or a vector. For character, window is a function name in the signal package, for example, 'hanning'; for a function, window takes one integer argument and returns a numeric vector with length of that input; for vectors, window is a numeric vector o length order+1.

Value

Filtered signals, vector if x is a vector, or matrix of the same dimension as x

Examples



t <- seq(0, 1, by = 0.0005)
x <- sin(t * 0.4 * pi) + sin(t * 4 * pi) + 2 * sin(t * 120 * pi)

oldpar <- par(mfrow = c(2, 2), mar = c(3.1, 2.1, 3.1, 0.1))
# ---- Using band_pass1 ------------------------------------------------

y1 <- band_pass1(x, 2000, 0.1, 1)
y2 <- band_pass1(x, 2000, 1, 5)
y3 <- band_pass1(x, 2000, 10, 80)

plot(t, x, type = 'l', xlab = "Time", ylab = "",
     main = "Mixture of 0.2, 2, and 60Hz")
lines(t, y1, col = 'red')
lines(t, y2, col = 'blue')
lines(t, y3, col = 'green')
legend(
  "topleft", c("Input", "Pass: 0.1-1Hz", "Pass 1-5Hz", "Pass 10-80Hz"),
  col = c(par("fg"), "red", "blue", "green"), lty = 1,
  cex = 0.6
)

# plot pwelch
pwelch(x, fs = 2000, window = 4000, noverlap = 2000, plot = 1)
pwelch(y1, fs = 2000, window = 4000, noverlap = 2000,
       plot = 2, col = "red")
pwelch(y2, fs = 2000, window = 4000, noverlap = 2000,
       plot = 2, col = "blue")
pwelch(y3, fs = 2000, window = 4000, noverlap = 2000,
       plot = 2, col = "green")


# ---- Using band_pass2 with FIR filters --------------------------------

order <- floor(2000 / 3)
z1 <- band_pass2(x, 2000, 0.1, 1, method = "fir", order = order)
z2 <- band_pass2(x, 2000, 1, 5, method = "fir", order = order)
z3 <- band_pass2(x, 2000, 10, 80, method = "fir", order = order)

plot(t, x, type = 'l', xlab = "Time", ylab = "",
     main = "Mixture of 0.2, 2, and 60Hz")
lines(t, z1, col = 'red')
lines(t, z2, col = 'blue')
lines(t, z3, col = 'green')
legend(
  "topleft", c("Input", "Pass: 0.1-1Hz", "Pass 1-5Hz", "Pass 10-80Hz"),
  col = c(par("fg"), "red", "blue", "green"), lty = 1,
  cex = 0.6
)

# plot pwelch
pwelch(x, fs = 2000, window = 4000, noverlap = 2000, plot = 1)
pwelch(z1, fs = 2000, window = 4000, noverlap = 2000,
       plot = 2, col = "red")
pwelch(z2, fs = 2000, window = 4000, noverlap = 2000,
       plot = 2, col = "blue")
pwelch(z3, fs = 2000, window = 4000, noverlap = 2000,
       plot = 2, col = "green")


# ---- Clean this demo --------------------------------------------------
par(oldpar)