My tuneR sawtooth wave function generator is broken.
When I use the sine function, I get exactly what I expect: a sine wave whose
frequency is defined by the freq parameter. In particular, higher frequencies
have shorter wavelengths (more cycles per second means shorter waves). When I
create a sawtooth wave, the opposite seems to occur: higher frequencies result
in longer waves. But that?s not all: as frequencies increase, it appears that
wavelengths increase to infinite length, then get shorter again as the wave
reverses, then it gets longer and flips again.
Here?s a small file that demonstrates the bad sawtooth waves:
library(tuneR)
sample_rate <- 12000
reverse <- FALSE
mycolors=c("red","orange","yellow","green","cyan","blue","violet","magenta")
plot(sawtooth(110,duration=round(sample_rate/100),samp.rate=sample_rate,xunit="samples")@left,type="l")
freqs <- c(111,112,113,114,115,116,117,118)
for (i in 1:length(freqs)) {
temp <-
sine(freqs[i],duration=round(sample_rate/100),samp.rate=sample_rate,xunit="samples")
lines(temp at left,type="l",lty=2,col=mycolors[i])
}
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Ccing the maintainer if the tuneR package. Looks to me like sawtooth (and square) don't behave as expected when using xunit="samples". Workaround is to use xunit="time" instead: sawtooth(110,duration=1/100,samp.rate=sample_rate,xunit="time") I looked at the code but found it to be opaque. -- Sent from my phone. Please excuse my brevity. On November 12, 2017 6:15:45 AM PST, Michael Tiemann <mdtiemann at gmail.com> wrote:>My tuneR sawtooth wave function generator is broken. > >When I use the sine function, I get exactly what I expect: a sine wave >whose frequency is defined by the freq parameter. In particular, >higher frequencies have shorter wavelengths (more cycles per second >means shorter waves). When I create a sawtooth wave, the opposite >seems to occur: higher frequencies result in longer waves. But that?s >not all: as frequencies increase, it appears that wavelengths increase >to infinite length, then get shorter again as the wave reverses, then >it gets longer and flips again. > >Here?s a small file that demonstrates the bad sawtooth waves: > >library(tuneR) > >sample_rate <- 12000 >reverse <- FALSE >mycolors=c("red","orange","yellow","green","cyan","blue","violet","magenta") >plot(sawtooth(110,duration=round(sample_rate/100),samp.rate=sample_rate,xunit="samples")@left,type="l") >freqs <- c(111,112,113,114,115,116,117,118) >for (i in 1:length(freqs)) { >temp <- >sine(freqs[i],duration=round(sample_rate/100),samp.rate=sample_rate,xunit="samples") > lines(temp at left,type="l",lty=2,col=mycolors[i]) >} > > > > > [[alternative HTML version deleted]] > >______________________________________________ >R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide >http://www.R-project.org/posting-guide.html >and provide commented, minimal, self-contained, reproducible code.
Here is perhaps a better sawtooth wave generator:
sawtooth <- function(freq, duration = samp.rate, from = 0, samp.rate 44100,
bit = 1,
stereo = FALSE, xunit = c("samples",
"time"), reverse
= FALSE, ...){
xunit <- match.arg(xunit)
durFrom <- preWaveform(freq = freq, duration = duration, from = from,
xunit = xunit, samp.rate = samp.rate)
channel <-
rep(seq(1,-1,length=samp.rate/freq),length=durFrom["duration"])
if(!is.logical(reverse) || length(reverse) != 1)
stop("'reverse' must be a logical value of length 1")
if(reverse) channel <- rev(channel)
postWaveform(channel = channel, samp.rate = samp.rate,
bit = bit, stereo = stereo, ...)
}
On Sun, Nov 12, 2017 at 6:57 PM, Jeff Newmiller <jdnewmil at
dcn.davis.ca.us>
wrote:
> Ccing the maintainer if the tuneR package.
>
> Looks to me like sawtooth (and square) don't behave as expected when
using
> xunit="samples". Workaround is to use xunit="time"
instead:
>
> sawtooth(110,duration=1/100,samp.rate=sample_rate,xunit="time")
>
> I looked at the code but found it to be opaque.
> --
> Sent from my phone. Please excuse my brevity.
>
> On November 12, 2017 6:15:45 AM PST, Michael Tiemann <mdtiemann at
gmail.com>
> wrote:
> >My tuneR sawtooth wave function generator is broken.
> >
> >When I use the sine function, I get exactly what I expect: a sine wave
> >whose frequency is defined by the freq parameter. In particular,
> >higher frequencies have shorter wavelengths (more cycles per second
> >means shorter waves). When I create a sawtooth wave, the opposite
> >seems to occur: higher frequencies result in longer waves. But that?s
> >not all: as frequencies increase, it appears that wavelengths increase
> >to infinite length, then get shorter again as the wave reverses, then
> >it gets longer and flips again.
> >
> >Here?s a small file that demonstrates the bad sawtooth waves:
> >
> >library(tuneR)
> >
> >sample_rate <- 12000
> >reverse <- FALSE
>
>mycolors=c("red","orange","yellow","green","cyan","blue",
> "violet","magenta")
> >plot(sawtooth(110,duration=round(sample_rate/100),samp.
> rate=sample_rate,xunit="samples")@left,type="l")
> >freqs <- c(111,112,113,114,115,116,117,118)
> >for (i in 1:length(freqs)) {
> >temp <-
> >sine(freqs[i],duration=round(sample_rate/100),samp.rate>
sample_rate,xunit="samples")
> > lines(temp at left,type="l",lty=2,col=mycolors[i])
> >}
> >
> >
> >
> >
> > [[alternative HTML version deleted]]
> >
> >______________________________________________
> >R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >https://stat.ethz.ch/mailman/listinfo/r-help
> >PLEASE do read the posting guide
> >http://www.R-project.org/posting-guide.html
> >and provide commented, minimal, self-contained, reproducible code.
>
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