就是关于置信区间的程序
<br />
f = function(n = 1000, alpha = 0.95, rn = 50) {<br />
d = replicate(n, rnorm(rn))<br />
m = colMeans(d)<br />
#s = apply(d, 2, sd)<br />
z = qnorm(1 - (1 - alpha) / 2)<br />
y0 = m - z * 1 / sqrt(50)<br />
y1 = m + z * 1 / sqrt(50)<br />
plot(1, xlim = c(0.5, n + 0.5), ylim = c(min(y0), max(y1)),<br />
type = "n", xlab = "", ylab = "")<br />
abline(h = 0, lty = 2)<br />
for (i in 1:n) {<br />
arrows(i, y0[i], i, y1[i], length = 0.05, angle = 90,<br />
code = 3, col = ifelse(0 > y0[i] & 0 < y1[i], "blue",<br />
"red"))<br />
points(i, m[i])<br />
Sys.sleep(.1)<br />
}<br />
Sys.sleep(3)<br />
}<br />
<br />
replicate(2, f(100,.95))<br />
<br />
想问: #s = apply(d, 2, sd) 这句是起什么作用的?