emuR (version 2.4.0)

cr: Plot digital sinuoids.

Description

The function plots and/or sums digital sinusoids for different parameter settings.

Usage

cr(
  A = 1,
  k = 1,
  p = 0,
  N = 16,
  samfreq = NULL,
  duration = NULL,
  const = NULL,
  expon = NULL,
  plotf = TRUE,
  ylim = NULL,
  xlim = NULL,
  values = FALSE,
  xlab = "Time (number of points)",
  ylab = "Amplitude",
  type = "b",
  bw = NULL,
  dopoints = FALSE,
  ...
)

Arguments

A

A vector of amplitude values. Defaults to A = 1

k

A vector of cycles (repetitions). Defaults to k = 1

p

A vector of phase values between -pi/2 and pi/2. Defaults to 0.

N

The number of points in the signal. Defaults to 16.

samfreq

If NULL, then a sinusoid is plotted with a frequency of k cycles per N points. Otherwise, if samfreq is an numeric, then the argument to k is interpreted as the frequency in Hz and the sinusoid at that frequency is plotted for however many points are specified by N. For example, if samfreq is 40 (Hz), and if N is 40 and k = 1, then 1 cycle of a 1 Hz sinusoid will be plotted.

duration

Specify the duration in ms. If NULL, the default, then the duration of the sinusoid is in points (N), otherwise if a numeric value is supplied, then in ms. For example, 1/2 second of a 1 cycle sinusoid at a sampling frequency of 40 Hz: duration = 500, k = 1, samfreq=40. A ms value can be supplied only if the sampling frequency is also specified.

const

A single numeric vector for shifting the entire sinusoid up or down the y-axis. For example, when const is 5, then 5 + s, where s is the sinusoid is plotted. Defaults to 0 (zero).

expon

A numeric vector. If supplied, then what is plotted is expon[j]\(\mbox{\textasciicircum}\)(c(0:(N - 1) * A cos (2 * pi * k/N * (0:(N-1))). For example, a decaying sinusoid is produced with cr(expon=-0.9). Defaults to NULL (i.e. to expon = 1).

plotf

A single-valued logical vector. If TRUE (default), the sinusoid is plotted.

ylim

A two-valued numeric vector for specifying the y-axis range.

xlim

A two-valued numeric vector for specifying the y-axis range.

values

If TRUE, then the values of the sinusoid are listed. Defaults to FALSE.

xlab

A character vector for plotting the x-axis title.

ylab

A character vector for plotting the y-axis title.

type

A character vector for specifying the line type (see par)

bw

A numeric vector for specifying the bandwidth, if the sampling frequency is supplied. The bandwidth is converted to an exponential (see expon using exp( - rad(bw/2, samfreq = samfreq).

dopoints

this is now redundant.

...

Option for supplying further graphical parameters - see par.

Author

Jonathan Harrington

See Also

crplot

Examples

# cosine wave
cr()

# doubling the frequency, 1/3 amplitude, phase = pi/4, 50 points
cr(A=1/3, k=2, p=pi/4, N=50)

# sum 3 sinusoids of different frequencies)
cr(k=c(1, 3, 4))

# sum 2 sinusoids of different parameters
cr(c(1, 2), c(2, 10), c(0, -pi/3), N=200, type="l")


# store the above to a vector and overlay with noise
v = cr(c(1, 2), c(2, 10), c(0, -pi/3), N=200, type="l", values=TRUE)
r = runif(200, -3, 3)
v = v+r
plot(0:199, v, type="l")


# 100 points of a 50 Hz sinusoid with a 4 Hz bandwidth 
# at a sampling frequency of 200 Hz
cr(k=50, bw=4, samfreq=2000, N=100)

# the same but shift the y-axis by +4 (d.c. offset=+4)
cr(const=4, k=50, bw=4, samfreq=2000, N=100)

# sinusoid multiplied by a decaying exponential (same effect as bandwidth)
cr(expon=-0.95,  N=200, type="l")