Re: [R] generate a vector of random numbers within confines of certain parameters

[Bert Gunter]

All floating point operations are done to machine precision -- roughly
16 digits. See ?.Machine . You can choose to round, truncate, or
display to anything less than that that you care to. See also the
digits parameter of  ?options

The rest of your post is ambiguous to me. But note that (all?/most?)
rng's are vectorized, so e.g.

> set.seed(1123)

> rnorm(10,mean= runif(10,2,3), sd = runif(10,4,6))

 [1]  4.369411  1.944876  3.143913  6.489048 -1.093468  1.330675
-3.936239 11.740755
 [9] -2.260413 -1.748759

... if that's what you meant.

Cheers,
Bert


Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Tue, Aug 2, 2016 at 11:56 AM, Adrian Johnson
 wrote:
> Dear group,
>
> I am trying to generate a vector of random numbers for 20K observation.
>
> however, I want to generate numbers (with 6 decimal places) within the range 
> of
> Std. Dev : 2-3
> mean  : 4-6
>
> Is there a method to generate numbers with 6 decimal places under
> these parameters
>
> thank you.
> Adrian
>
> __
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> 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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and provide commented, minimal, self-contained, reproducible code.

Re: [R] generate a vector of random numbers within confines of certain parameters

[Jeff Newmiller]

x <- rnorm( 2, 5, 2.5 )

The requirement for "random" is ill-specified because it omits mention of which 
random distribution you want (I assumed normal distribution above).

The requirement for "decimal places" is ill-defined because floating point 
numbers are internally represented with mantissa and exponent ("scientific 
notation"), so large numbers have fewer significant "decimal places" in the 
fraction than small numbers do. For most purposes double precision IEEE754 
numbers have more precision than you will need. What gets sticky is if you want 
to LIMIT the number of decimals... you may need to use the sprintf function and 
export the data as character values if that is important (which I doubt).

Note that the default behavior of the R console is to PRINT values with four 
decimals, but the rest of the significant digits are really still there. 
-- 
Sent from my phone. Please excuse my brevity.

On August 2, 2016 11:56:35 AM PDT, Adrian Johnson  
wrote:
>Dear group,
>
>I am trying to generate a vector of random numbers for 20K observation.
>
>however, I want to generate numbers (with 6 decimal places) within the
>range of
>Std. Dev : 2-3
>mean  : 4-6
>
>Is there a method to generate numbers with 6 decimal places under
>these parameters
>
>thank you.
>Adrian
>
>__
>R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.

__
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Re: [R] generate a vector of random numbers within confines of certain parameters

[David L Carlson]

The second one (x2) uses the same mean/sd for the 2 variates. If you want 
to change the mean/sd for each variate:

> x3 <- round(replicate(2, rnorm(1, runif(1, 4, 6), runif(1, 2, 3))), 6)
> head(x3)
[1] 5.648530 5.689563 2.945512 3.915723 8.527447 0.298535

---
David C

-Original Message-
From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of David L Carlson
Sent: Tuesday, August 2, 2016 2:40 PM
To: Adrian Johnson; r-help
Subject: Re: [R] generate a vector of random numbers within confines of certain 
parameters

Try

> set.seed(42)
> x1 <- round(rnorm(2, 4, 2), 6)
> head(x1)
[1] 6.741917 2.870604 4.726257 5.265725 4.808537 3.787751

Setting the seed makes the sequence reproducible, but if that is not important, 
you can leave it out. This assumes you want a normal distribution and you want 
to specify the mean and standard deviation. If you want those to be selected 
randomly. The following does that using uniform distributions so each mean and 
standard deviation is equally likely within the range:

> x2 <- round(rnorm(2, runif(1, 4, 6), runif(1, 2, 3)), 6)
> head(x2)
[1] 4.054289 4.745569 5.795536 6.316750 4.370713 5.586646

-
David L Carlson
Department of Anthropology
Texas A University
College Station, TX 77840-4352




-Original Message-
From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Adrian Johnson
Sent: Tuesday, August 2, 2016 1:57 PM
To: r-help
Subject: [R] generate a vector of random numbers within confines of certain 
parameters

Dear group,

I am trying to generate a vector of random numbers for 20K observation.

however, I want to generate numbers (with 6 decimal places) within the range of
Std. Dev : 2-3
mean  : 4-6

Is there a method to generate numbers with 6 decimal places under
these parameters

thank you.
Adrian

__
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

__
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

__
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Re: [R] generate a vector of random numbers within confines of certain parameters

[David L Carlson]

Try

> set.seed(42)
> x1 <- round(rnorm(2, 4, 2), 6)
> head(x1)
[1] 6.741917 2.870604 4.726257 5.265725 4.808537 3.787751

Setting the seed makes the sequence reproducible, but if that is not important, 
you can leave it out. This assumes you want a normal distribution and you want 
to specify the mean and standard deviation. If you want those to be selected 
randomly. The following does that using uniform distributions so each mean and 
standard deviation is equally likely within the range:

> x2 <- round(rnorm(2, runif(1, 4, 6), runif(1, 2, 3)), 6)
> head(x2)
[1] 4.054289 4.745569 5.795536 6.316750 4.370713 5.586646

-
David L Carlson
Department of Anthropology
Texas A University
College Station, TX 77840-4352




-Original Message-
From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Adrian Johnson
Sent: Tuesday, August 2, 2016 1:57 PM
To: r-help
Subject: [R] generate a vector of random numbers within confines of certain 
parameters

Dear group,

I am trying to generate a vector of random numbers for 20K observation.

however, I want to generate numbers (with 6 decimal places) within the range of
Std. Dev : 2-3
mean  : 4-6

Is there a method to generate numbers with 6 decimal places under
these parameters

thank you.
Adrian

__
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

__
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

[R] generate a vector of random numbers within confines of certain parameters

[Adrian Johnson]

Dear group,

I am trying to generate a vector of random numbers for 20K observation.

however, I want to generate numbers (with 6 decimal places) within the range of
Std. Dev : 2-3
mean  : 4-6

Is there a method to generate numbers with 6 decimal places under
these parameters

thank you.
Adrian

__
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.