Interpolate / Increase the sample rate
Upsample a signal by a constant factor by using an FIR filter to interpolate between points.
interp(x, q, n = 4, Wc = 0.5)
x |
the signal to be upsampled. |
q |
the integer factor to increase the sampling rate by. |
n |
the FIR filter length. |
Wc |
the FIR filter cutoff frequency. |
It uses an order 2*q*n+1 FIR filter to interpolate between samples.
The upsampled signal, an array of length q * length(x).
Original Octave version by Paul Kienzle pkienzle@user.sf.net. Conversion to R by Tom Short.
Octave Forge http://octave.sf.net
# The graph shows interpolated signal following through the # sample points of the original signal. t <- seq(0, 2, by = 0.01) x <- chirp(t, 2, 0.5, 10, 'quadratic') + sin(2*pi*t*0.4) y <- interp(x[seq(1, length(x), by = 4)], 4, 4, 1) # interpolate a sub-sample plot(t, x, type = "l") idx <- seq(1,length(t),by = 4) lines(t, y[1:length(t)], col = "blue") points(t[idx], y[idx], col = "blue", pch = 19)
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