我的R代码:
bnc1<-function(maxITR=100000, d=2, l=1){
counts=0;
for (i in 1:maxITR){
x=runif(1,0,pi);
y=runif(2,0,d/2);
if ((l/2*sin(x)) >= y) counts=counts+1;
}
counts/maxITR*d/l
}
运行代码:
> bnc1(maxITR=1000)
[1] 0.652
There were 50 or more warnings (use warnings() to see the first 50)
> warnings()
Warning messages:
1: In if ((l/2 * sin(x)) >= y) counts = counts + 1 ... :
the condition has length > 1 and only the first element will be used
2: In if ((l/2 * sin(x)) >= y) counts = counts + 1 ... :
the condition has length > 1 and only the first element will be used
...
49: In if ((l/2 * sin(x)) >= y) counts = counts + 1 ... :
the condition has length > 1 and only the first element will be used
50: In if ((l/2 * sin(x)) >= y) counts = counts + 1 ... :
the condition has length > 1 and only the first element will be used
有没有人知道导致警告的原因?
答案 0 :(得分:6)
runif
返回一个向量。
if
只取一个值(不是矢量)。
查看runif
的手册,我认为您没有正确使用它。
在R中,删除for循环并使用向量通常是有意义的 - 例如:
bnc1<-function(maxITR=100000, d=2, l=1){
x=runif(maxITR,0,pi);
y=runif(maxITR,0,d/2);
counts = sum((l/2*sin(x)) >= y);
counts/maxITR*d/l
}