periodogram-methods {tuneR} | R Documentation |
This function estimates one or more periodograms (spectral densities)
of the time series contained in an object of class Wave
(or directly in a Wave file)
using a window running through the time series (possibly with overlapping).
It returns an object of class Wspec
.
periodogram(object, ...) ## S4 method for signature 'Wave': periodogram(object, width = length(object), overlap = 0, starts = NULL, ends = NULL, taper = 0, normalize = TRUE, frqRange = c(-Inf, Inf), ...) ## S4 method for signature 'character': periodogram(object, width, overlap = 0, from = 1, to = Inf, units = c("samples", "seconds", "minutes", "hours"), downsample = NA, channel = c("left", "right"), pieces = 1, ...)
object |
An object of class Wave or a character string pointing to a Wave file. |
width |
A window of width ‘width ’ running through the time series selects the samples
from which the periodograms are to be calculated. |
overlap |
The window can be applied by each overlapping overlap samples. |
starts |
Start number (in samples) for a window.
If not given, this value is derived from argument ends ,
or will be derived width and overlap . |
ends |
End number (in samples) for a window.
If not given, this value is derived from argument starts ,
or will be derived from width and overlap . |
taper |
proportion of data to taper. See spec.pgram for details. |
normalize |
Logical; if TRUE (default), two steps will be applied:
(i) the input signal will be normalized to amplitude max(abs(amplitude)) == 1 ,
(ii) the resulting spec values will be normalized to sum up to one for each periodogram. |
frqRange |
Numeric vector of two elements indicating minimum and maximum of the frequency range that is to be stored in the resulting object. This is useful to reduce memory consumption. |
from |
Where to start reading in the Wave file, in units . |
to |
Where to stop reading in the Wave file, in units . |
units |
Units in which from and to is given, the default is “samples”,
but can be set to time intervals such as “seconds”, see the Usage Section above. |
downsample |
Sampling rate the object is to be downsampled to.
If NA , the default, no changes are applied. Otherwise downsample must be in [2000, 192000] ;
typical values are 11025, 22050, and 44100 for CD quality. See also downsample . |
channel |
Character, indicating whether the “left” or “right” channel should be extracted
(see mono for details) - stereo processing is not yet implemented. |
pieces |
The Wave file will be read in in pieces steps in order to reduce the amount
of required memory. |
... |
Further arguments to be passed to the underlying function spec.pgram . |
An object of class Wspec
is returned containing the following slots.
freq |
Vector of frequencies at which the spectral density is estimated.
See spectrum for details. (1) |
spec |
List of vectors or matrices of the spec values returned by spec.pgram
at frequencies corresponding to freq .
Each element of the list corresponds to one periodogram estimated from samples of the window
beginning at start of the Wave object. |
kernel |
The kernel argument, or the kernel constructed from spans returned by spec.pgram . (1) |
df |
The distribution of the spectral density estimate can be approximated by a chi square distribution with
df degrees of freedom. (1) |
taper |
The value of the taper argument. (1) |
width |
The value of the width argument. (1) |
overlap |
The value of the overlap argument. (1) |
normalize |
The value of the normalize argument. (1) |
starts |
If the argument starts was given in the call, its value.
If the argument ends was given in the call, ‘ends - width ’.
If neither starts nor ends was given, the start points of all periodograms.
In the latter case the start points are calculated from the arguments width and overlap . |
stereo |
Whether the underlying Wave object was stereo ot not. (1) |
samp.rate |
Sampling rate of the underlying Wave object . (1) |
variance |
The variance of samples in each window, corresponding to amplitude / loudness of sound. |
energy |
The “energy” E, also an indicator for the amplitude / loudness of sound:
E(x_I) := 20 * log_{10} sum_{j in I} |x_j|,
where I indicates the interval I:= |
Those slots marked with “(1)” contain the information once, because it is unique for all periodograms of estimated by the function call.
Support for processing of stereo Wave
objects has not yet been implemented.
Uwe Ligges, ligges@statistik.tu-dortmund.de
Wspec
,
plot-Wspec
,
spec.pgram
,
Wave
.
# constructing a Wave object (1 sec.) containing sinus sound with 440Hz: Wobj <- sine(440, bit = 16) Wobj # Calculate periodograms in windows of 4096 samples each - without # any overlap - resulting in an Wspec object that is printed: Wspecobj <- periodogram(Wobj, width = 4096) Wspecobj # Plot the first periodogram from Wspecobj: plot(Wspecobj) # Plot the third one and choose a reasonable xlim: plot(Wspecobj, which = 3, xlim = c(0, 1000)) # Mark frequency that has been generated before: abline(v = 440, col="red") FF(Wspecobj) # all ~ 440 Hertz noteFromFF(FF(Wspecobj)) # all diapason a