Decimate with 'FIR' or 'IIR' filter

Usage

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

Arguments

x: signal to be decimated
q: integer factor to down-sample by
n: filter order used in the down-sampling; default is 30 if ftype='fir', or 8 if ftype='iir'
ftype: filter type, choices are 'fir' (default) and 'iir'

Value

Decimated signal

Details

This function is migrated from signal package, but with bugs fixed on 'FIR' filters. The result agrees with 'Matlab' decimate function with 'FIR' filters. Under 'IIR' filters, the function is identical with signal::decimate, and is slightly different with 'Matlab' version.

Examples


x <- 1:100
y <- decimate(x, 2, ftype = "fir")
y
#>  [1]  1  3  5  7  9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49
#> [26] 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99

# compare with signal package
z <- signal::decimate(x, 2, ftype = "fir")

# Compare decimated results
plot(x, type = 'l')
points(seq(1,100, 2), y, col = "green")
points(seq(1,100, 2), z, col = "red")