Error with generating sequences when graphing plots in R

Question

Simply trying to generate a function for plotting area under the curve for a z score or set of z scores, but when I give two z scores with zshade(c(1,2)) I get the following error:

Error in seq.default(z1, z2, 0.01) : 'to' must be of length 1

But I'm not sure why this is the case, I double checked z2 and it's indeed of length 1 so I'm unsure where the error is.

zshade = function(z, shade = "left") {
  # If more than 2 z scores are given
  if (length(z) > 2) {
    stop("Error: Too many z scores given!")
  }

  # If two z scores are given
  if (length(z) > 1) {
    z1 = min(z)
    z2 = max(z)
    cord.x = c(z1, seq(z1, z2, 0.01), z2)
    cord.y = c(0, dnorm(seq(z1, z2, 0.01)), 0)
    curve(dnorm(x, 0, 1), xlim = c(-4, 4), main = "Standard Normal", 
      ylab = "", xlab = "")
    polygon(cord.x, cord.y, col = "skyblue")
  }

  # If a single z score is given
  if (shade == "left") {
    z1 = -4
    z2 = z
    cord.x = c(z1, seq(z1, z2, 0.01), z2)
    cord.y = c(0, dnorm(seq(z1, z2, 0.01)), 0)
    curve(dnorm(x, 0, 1), xlim = c(-4, 4), main = "Standard Normal Curve", 
        ylab = "", xlab = "")
    polygon(cord.x, cord.y, col = "skyblue")
  }
  if (shade == "right") {
    z1 = z
    z2 = 4
    cord.x = c(z1, seq(z1, z2, 0.01), z2)
    cord.y = c(0, dnorm(seq(z1, z2, 0.01)), 0)
    curve(dnorm(x, 0, 1), xlim = c(-4, 4), main = "Standard Normal Curve", 
        ylab = "", xlab = "")
    polygon(cord.x, cord.y, col = "skyblue")
  }
}

zshade(c(1,2))

Answer 1

Silly mistake, see code below...

zshade = function(z, shade = "left") {
# If more than 2 z scores are given
if (length(z) > 2) {
  stop("Error: Too many z scores given!")
}

# If two z scores are given
if (length(z) > 1) {
  z1 = min(z)
  z2 = max(z)
  cord.x = c(z1, seq(z1, z2, 0.01), z2)
  cord.y = c(0, dnorm(seq(z1, z2, 0.01)), 0)
  curve(dnorm(x, 0, 1), xlim = c(-4, 4), main = "Standard Normal", 
        ylab = "", xlab = "")
  polygon(cord.x, cord.y, col = "skyblue")
}

if (length(z)==1) {
  # If a single z score is given
  if (shade == "left") {
    z1 = -4
    z2 = z
    cord.x = c(z1, seq(z1, z2, 0.01), z2)
    cord.y = c(0, dnorm(seq(z1, z2, 0.01)), 0)
    curve(dnorm(x, 0, 1), xlim = c(-4, 4), main = "Standard Normal Curve", 
          ylab = "", xlab = "")
    polygon(cord.x, cord.y, col = "skyblue")
  }
  if (shade == "right") {
    z1 = z
    z2 = 4
    cord.x = c(z1, seq(z1, z2, 0.01), z2)
    cord.y = c(0, dnorm(seq(z1, z2, 0.01)), 0)
    curve(dnorm(x, 0, 1), xlim = c(-4, 4), main = "Standard Normal Curve", 
          ylab = "", xlab = "")
    polygon(cord.x, cord.y, col = "skyblue")
  }
 }
}