[R] Writing program for these
Ben Bolker
bbolker at gmail.com
Thu Jan 27 16:22:21 CET 2011
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[cc'ing back to r-help]
On 01/27/2011 10:06 AM, Ben Boyadjian wrote:
> Yes the it says the uniform distribution on the interval (-5,5).
If this is real-valued (which again is not precisely defined, but
that would be how I would interpret) then the probability of choosing an
integer is again zero. With double-precision floating point values it
is not zero but is extremely small.
>
> This is what I have done for Question 2
> There is the trim function that can give the answer but I am meant to
> write the program. My question is whether I use the 0.05 or the 0.1. I
> dont want anything below the 5% and above the 95%.
Why not look at ?mean for the answer? Or compare the answer from
using mean with the 'trim' argument to the alternative solution you
listed below?
>
> # We first simulate 1000 observations .....
>
> x<-rt(1000,3)
> mean(x,trim=0.05) #or 0.1 I am not sure
> z<-sort(x)
> #next use either
> y<-z[-c(1:50,951:1000)] # We want the bottom 5% and top 5% so this
> corresponds to the elements that we are taking away.
> #or
> #y<-z[-c(1:100,901:1000)]
> mean(y)
>
> --------------------------------------------------
> From: "Ben Bolker" <bbolker at gmail.com>
> Sent: Thursday, January 27, 2011 2:24 PM
> To: <r-help at stat.math.ethz.ch>
> Subject: Re: [R] Writing program for these
>
>> Ben Boyadjian <benjy_cy_21 <at> hotmail.com> writes:
>>
>>>
>>> Hello I am trying to solve these problems and I am not allowed to use
>>> loops or
>> ifs.
>>>
>>> 1st Question
>>> My first question is that I have generated 100 random numbers from
>>> the uniform
>> distribution then
>>> A)add only the negative integers.
>>> B)add elements until the first appearance of a negative element.
>>>
>>> I know how to choose the negative elements for A but how to find
>>> integers?
>>
>> If this is the standard uniform U(0,1) distribution (which I assume
>> from your phrase "*the* uniform distribution" (emphasis added))
>> then there will be no integers in the sample ... ??
>>
>>> And I dont know what to do for B.
>>>
>>> 2nd Question
>>> Simulate 1000 observations from the student-t distribution with 3
>>> degrees of
>> freedom and then calculate
>>> the truncated mean by excluding bottom 5% and top 5%.
>>
>> Looks like homework questions, which are not answered on this list.
>> Please read the posting guide; if these are *not* homework questions,
>> please give us a plausible context. (Even if these are not homework
>> questions, the posting guide asks that you "do your homework" in a
>> broader sense by indicating what steps you have taken to solve your
>> problem on your own before posting.)
>>
>> One hint for the second question: ?rt
>>
>> good luck,
>> Ben Bolker
>>
>> ______________________________________________
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>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
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