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#' function to generate input singals (rgs/rbs/prbs/sine)
#'
#' \code{idinput} is a function for generating input signals (rgs/rbs/prbs/sine) for identification purposes
#'
#' @param n integer length of the input singal to be generated
#' @param type the type of input signal to be generated.
#' 'rgs' - generates random gaussian signal
#' 'rbs' - generates random binary signal
#' 'prbs' - generates pseudorandom binary signal
#' 'sine' - generates a signal that is a sum of sinusoids
#'
#' Default value is type='rgs'
#' @param band determines the frequency content of the signal.
#' For type='rbs'/'sine'/, band = [wlow,whigh]
#' which specifies the lower and the upper bound of the passband frequencies(expressed as fractions of Nyquist frequency). Default is c(0,1)
#' For type='prbs', band=[0,B]
#' where B is such that the singal is constant over 1/B (clock period). Default is c(0,1)
#' @param levels row vector defining the input level. It is of the form
#' levels=c(minu, maxu)
#' For 'rbs','prbs', 'sine', the generated signal always between minu and maxu.
#' For 'rgs', minu=mean value of signal minus one standard deviation and maxu=mean value of signal plus one standard deviation
#'
#' Default value is levels=c(-1,1)
#'
#' @export
idinput<-function(n,type='rgs',band=c(0,1),levels=c(-1,1)){
if(type=="rbs"){
v1<-gen.rbs(n,band,levels)
}
else if(type=="rgs"){
v1<-gen.rgs(n,band,levels)
}
return(v1)
}
gen.rgs<-function(n,band,levels){
mu<-(levels[1]+levels[2])/2
sigma<-(levels[2]-levels[1])/2
v<-rnorm(n,mu,sigma)
v<-sapply(v, function(x) {if(x==0) rnorm(1) else x})
gfilt<-signal::butter(8,band,type ='pass',plane ='z')
v1<-signal::filter(gfilt,v)
return(v1)
}
gen.rbs<-function(n,band,levels){
v<-rnorm(n)
v<-sapply(v, function(x) {if(x==0) rnorm(1) else x}, simplify = 'vector')
#if we do not specify else case, it assigns it as NULL
bfilt<-signal::butter(8,band,type = 'pass',plane = 'z')
v1<-signal::filter(bfilt,v)
v1<-sapply(v1, function(x) {ifelse(x>0 , levels[2] , levels[1]) })
return(v1)
}
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