d[1] = 1
d[2] = 1
for(i in 3:20){
d[i] = d[i-1]+d[i-2]
print(d[i])}  

e = rep(0, 10)

e[1] = 1
e[2] = 1
i = 3
while (i<=10){
e[i] = e[i-1] + e[i-2]
i=i+1
}
print(e)

f = c(1,2,3,4,5,1,2,6,11)
g = c()
for(i in 1:length(f))
# 条件语句
{
if(f[i]==1) g[i]="a"
else if(f[i]==2) g[i]="b"
else g[i]="c"
}

h = function(a=1,b=2)  # a, b 关键字参数
{x = seq(-1,1, 0.2)  # 生成等差数列
y = a*x + b
plot(x,y)}  # 画图
h()
h(3,4)