Defining a variable inside a loop inside a function-CodePudding

So I have an assignment, where I have to show the convergence of regression coefficients to a certain value if the observed variable has a measurement error. The idea is to show the convergence depending on the number of observations as well as on the standard deviations of the variables.

I built the following function that should create a matrix with the regression coefficients depending on the number of observations. In a later step I would want to show this in a plot and then in a shiny webapp.

The function is:

Deviation <- function(N, sd_v = 1, sd_u = 1, sd_w = 1){
  b_1 <- 1
  b_2 <- 2
  for ( j in length(1:N)){
    v <- rnorm(j, mean = 0, sd_v)
    u <- rnorm(j, mean = 0, sd_u)
    w <- rnorm(j, mean = 0, sd_w)
    X <- u   w
    Y <- b_1   b_2 * X   v
    Reg <- lm(Y~X)
    if (j==1) {
      Coeffs <- matrix(Reg$coefficients)
    } else {
      Coeffs <- rbind(Coeffs, Reg$coefficients)  
    }
  }
  Coeffs <- as.data.frame(Coeffs)
  return(Coeffs)  
}
Deviation(100)

I always get the error that the variable Coeffs is not defined...

Thanks in advance!

CodePudding user response：

As pointed out in the discussion, one possible solution is to change the length(1:N), to simply 1:Nas written below. This works for me.

Deviation <- function(N, sd_v = 1, sd_u = 1, sd_w = 1){
  b_1 <- 1
  b_2 <- 2
  for ( j in 1:N){
    v <- rnorm(j, mean = 0, sd_v)
    u <- rnorm(j, mean = 0, sd_u)
    w <- rnorm(j, mean = 0, sd_w)
    X <- u   w
    Y <- b_1   b_2 * X   v
    Reg <- lm(Y~X)
    if (j==1) {
      Coeffs <- matrix(Reg$coefficients)
    } else {
      Coeffs <- rbind(Coeffs, Reg$coefficients)  
    }
  }
  Coeffs <- as.data.frame(Coeffs)
  return(Coeffs)  
}

followed by...

Deviation(100)