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#跑出一樣本數為n的布朗運動圖nIter張，512張太多了會當，改為3張
Brownian <- function(n = 11, pause = 0.05, nIter = 3, ...) {
x = rnorm(n)
y = rnorm(n)
i = 1
while (i <= nIter) {
plot(x, y, ...)
text(x, y, cex = 0.5)
x = x + rnorm(n)
y = y + rnorm(n)
##當作系統暫停Sys.sleep()的秒數，右大括號，表示迴圈結束
Sys.sleep(pause)
i = i + 1
}
}
###
## test it畫圖出來
Brownian(xlim = c(-20, 20), ylim = c(-20, 20),
pch = 21, cex = 2, col = "cyan", bg = "lavender")
###
##不使用while迴圈的寫法，參考網路作法，原來是用repeat代替，如果拿掉i <= nIter的張數指令，剩下隨機rnorm(n)的話，指令會卡住而無法繼續跑，設定nIter = 3張，卻不知道為何最後只有出現2張，是因為if(i >= nIter) break...
Brownian <- function(n = 20, pause = 0.05, nIter = 3, ...) {
x = rnorm(n)
y = rnorm(n)
i = 1
repeat {
plot(x, y, ...)
text(x, y, cex = 0.5)
x = x + rnorm(n)
y = y + rnorm(n)
Sys.sleep(pause)
i = i + 1
if(i >= nIter) break
}
}
Brownian(xlim = c(-20, 20), ylim = c(-20, 20),
pch = 21, cex = 2, col = "cyan", bg = "lavender")
