在函数中设置默认值?

I have a simple density function below:

下面是一个简单的密度函数:

dpower <- function(x, b, r){
if ((b <= 0 | r <= 0)) 
return("Wrong parameters entered!")
else{
 density.temp <- (r/b)*(x/b)^(r - 1)
 density.temp[which(x >= b | x <= 0)] <- NA
 return(density.temp)
 } 
}

This function returns density corresponding to value x from the specified distribution with parameters b and r. I'd like to set the default value on x that if the user doesn't specify x, the default values passes through. We can simply set dpower <- function(x = x.default, b, r)... however, my default value depends on r and b. How can I do that? suppose the default value for x is:

这个函数返回与参数b和r值对应的值x对应的密度。我想在x上设置默认值，如果用户不指定x，默认值就会通过。我们可以简单地设置dpower <- function(x = x.default, b, r)…但是，我的默认值依赖于r和b，我该怎么做呢?假设x的默认值是:

seq(from = 0.05, to = b, by = 0.001)

Thanks for your help,

谢谢你的帮助,

2 个解决方案

#1

dpower <- function(b, r, x = seq(from = 0.05, to = b, by = 0.001))
....

#2

You can set the value of X to NULL and have one of the first lines of your function be

您可以将X的值设为NULL，并拥有函数的第一行。

 if(is.null(x))
     x <- seq(from = 0.05, to = b, by = 0.001)