interp {gsignal}

Interpolation

Description

Increase sample rate by integer factor.

Usage

interp(x, q, n = 4, Wc = 0.5)

Arguments

x

input data, specified as a numeric vector.

q

interpolation factor, specified as a positive integer.

n

Half the number of input samples used for interpolation, specified as a positive integer. For best results, use n no larger than 10. The low-pass interpolation filter has length 2 × n × q + 1. Default: 4.

Wc

Normalized cutoff frequency of the input signal, specified as a positive real scalar not greater than 1 that represents a fraction of the Nyquist frequency. A value of 1 means that the signal occupies the full Nyquist interval. Default: 0.5.

Value

interpolated signal, returned as a vector.

Author(s)

Paul Kienzle, [e-mail].
Conversion to R by Geert van Boxtel [e-mail].

See Also

decimate, resample

Examples

# Generate a signal
t <- seq(0, 2, 0.01)
x <- chirp(t, 2, .5, 10,'quadratic') + sin(2 * pi * t * 0.4)
w <- seq(1, 121, 4)
plot(t[w] * 1000, x[w], type = "h", xlab = "", ylab = "")
points(t[w] * 1000, x[w])
abline (h = 0)
y <- interp(x[seq(1, length(x), 4)], 4, 4, 1)
lines(t[1:121] * 1000, y[1:121], type = "l", col = "red")
points(t[1:121] * 1000, y[1:121], col = "red", pch = '+')
legend("topleft", legend = c("original", "interpolated"),
  lty = 1, pch = c(1, 3), col = c(1, 2))