decimate: Decimate or downsample a signal

View source: R/decimate.R

decimateR Documentation

Decimate or downsample a signal


Downsample a signal by a factor, using an FIR or IIR filter.


decimate(x, q, n = if (ftype == "iir") 8 else 30, ftype = "iir")



signal to be decimated.


integer factor to downsample by.


filter order used in the downsampling.


filter type, "iir" or "fir"


By default, an order 8 Chebyshev type I filter is used or a 30-point FIR filter if ftype is 'fir'. Note that q must be an integer for this rate change method.

Makes use of the filtfilt function with all its limitations.


The decimated signal, an array of length ceiling(length(x) / q).


Original Octave version by Paul Kienzle Conversion to R by Tom Short.


Octave Forge

See Also

filter, resample, interp


# The signal to decimate starts away from zero, is slowly varying
# at the start and quickly varying at the end, decimate and plot.
# Since it starts away from zero, you will see the boundary
# effects of the antialiasing filter clearly.  You will also see
# how it follows the curve nicely in the slowly varying early
# part of the signal, but averages the curve in the quickly
# varying late part of the signal.
t <- seq(0, 2, by = 0.01)
x <- chirp(t, 2, 0.5, 10, 'quadratic') + sin(2*pi*t*0.4)
y <- decimate(x, 4)   # factor of 4 decimation
plot(t, x, type = "l")
lines(t[seq(1,length(t), by = 4)], y, col = "blue")

signal documentation built on June 26, 2024, 9:06 a.m.

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