[R] protentially serious R error

[liuxf]

Hi guy,
I have recently encountered a problem while  I was just trying to generate
some random numbers with the function "rnorm", the problem is shown below:
########case 1############
> rnorm(20*0.2)
[1] -1.2765922 -0.5732654 -1.2246126 -0.4734006
########case 2###########
*> rnorm(20*(1-0.8))
[1] -0.62036668  0.04211587 -0.91092165*
#########case 3############
> a<-0.2
> rnorm(20*a)
[1]  0.1580288 -0.6545846  1.7672873  0.7167075
#############case 4#########
*> b<-1-0.8
> rnorm(20*b)
[1] 0.9101742 0.3841854 1.6821761*

I was expecting the 4 cases should do the same job--generate 4 random
numbers. But in case 2 and 4 I only get 3. Has anyone else seen this problem
before? Thanks. (I have tried with other functions i.e "rchisq","rexp" ...)
#######################################################################
One of my colleague also have a problem that we think it might be related
with the problem I addressed above:

> test1 <- runif(10,0,1)
> test1
 [1] 0.3868379 0.1587814 0.8140483 0.7796691 0.5357628 0.2431110 0.1782747
0.3906829 0.5262615 0.7440143
> test2 <- NULL
> for(i in seq(0.01,1,length=100)){
+   test2[i*100] <- sum(test1<i) 
+ }
> test2
  [1]  0  0  0  0  0  0 *NA*  0  0  0  0  0  0  0  0  1  1  2  2  2  2  2  2
2  3  3  3  3  3  3  3  3  3  3  3  3  3  3  4  5  5  5  5  5
 [45]  5  5  5  5  5  5  5  5  6  7  7  7  7  7  7  7  7  7  7  7  7  7  7
7  7  7  7  7  7  7  8  8  8  9  9  9  9 10 10 10 10 10 10 10
 [89] 10 10 10 10 10 10 10 10 10 10 10 10

Every time he re-runs the code there always always a "NA"(highlighted). Does
any one know why?  Your help is greatly appreciated.   


Xiaofeng





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