### pdfs, cdfs, quantiles, ecdf

# pdf of the standard normal

z <- seq(-4,4,0.01)		# seq() produces a sequence of numbers

y <- dnorm(z)

plot(z,y,type="l",main="pdf of the standard normal")

# cdf of the standard normal

p <- pnorm(z)

plot(z,p,type="l",main="cdf of the standard normal")

# quantiles of the standard normal

qnorm(0.50)		# median
qnorm(0.025)		# the 2.5% value
qnorm(0.975)		# the 97.5% value

# make the same plots for the Normal(mu = 65, sigma=3) distribution.

# make the same plots for the exponential distribution.

# For the voter participation by state in the 1844 Presidential Election plot its ecdf

part <- c(67.5,65.6,65.7,59.3,39.8,
	76.1,73.6,81.6,75.5,85.0,
	80.3,54.5,79.1,94.0,80.3,
	89.6,44.7,82.7,89.7,83.6,
	84.9,76.3,74.7,68.8,79.3)

hist(part)	

z <- (part - mean(part))/stdev(part)

cdf.compare(z, dist="normal")

quantile(part, 0.50)