# R/sim_dlf.R In dlim: Distributed Lag Interaction Model

#### Documented in sim_dlf

```#' Simulate Distributed Lag Functions
#' @description generate true distributed lag function values for a given type of simulation
#' @seealso Type \code{vignette('dlimOverview')} for a detailed description.
#' @export
#' @importFrom stats dnorm
#' @param L Number of lags minus 1
#' @param modifiers Vector of modifiers
#' @param type Effect modification simulation type: 1 is no modification, 2 is linear scale modification, 3 is non-linear shift modification, 4 is types 2 and 3 combined
#' @return This function returns the true distributed lag function values (class "\code{numeric}")

sim_dlf <- function(L,modifiers,type){
method<-"normal"
width <- 5
lags <- 0:L

0.2*pmax(1- ((l-center)^2)/100,0)
}else if(method=="normal"){
2.5*dnorm(l,center,width)
}
}

betas_l <- curve(lags,20, method=method)

if(type==1){ #no modification
betas <- matrix(rep(betas_l,length(modifiers)),nrow=L+1,byrow = FALSE) #lag x obs
}else if(type==2){ #linear scale modification
betas <- sweep(matrix(rep(((modifiers+1)/2),L+1),nrow=L+1,byrow = TRUE), MARGIN=1, betas_l, `*`)
}else if(type==3){ #logistic shift modification
centers <- 37/(1+exp(-20*(modifiers-0.5)))
if(length(modifiers)==1){
betas <- as.matrix(sapply(lags,curve,center=centers, method=method))
}else{
betas <- t(sapply(lags,curve,center=centers, method=method))
}
}else if(type==4){ #type 2 and type 3
centers <- 37/(1+exp(-20*(modifiers-0.5)))
if(length(modifiers)==1){
betas_l <- as.matrix(sapply(lags,curve,center=centers, method=method))
betas <- matrix(rep(((modifiers+1)/2),L+1),nrow=L+1,byrow = TRUE) * betas_l
}else{
betas_l <- t(sapply(lags,curve,center=centers, method=method))
betas <- matrix(rep(((modifiers+1)/2),L+1),nrow=L+1,byrow = TRUE) * betas_l
}
}else{
stop("Incorrect simulation type entered. Choose a type between 1 and 4. See ?dlim::sim_data for more information.")
}

return(betas)
}
```

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dlim documentation built on May 29, 2024, 8:32 a.m.