R help - Apr 2006 - how to control the data type

Hello:
I am generating a random number with rnorm(1). The generated number
has 8 decimals. I don't want so many decimals. How to control the
number of decimals in R?
Thanks!

Zhongmiao Wang

On 20 April 2006 at 22:00, zhongmiao wang wrote:
| Hello:
| I am generating a random number with rnorm(1). The generated number
| has 8 decimals. I don't want so many decimals. How to control the
| number of decimals in R?

You must have installed the professional version of R, just downgrade to the
home version which has only four digits precision.

Seriously, your equating display precision with the representation -- which
is not correct.  Consider:
> a <- 1/3
> print(a)
[1] 0.3333333
> print(a, digits=18)
[1] 0.333333333333333315

where the second print statement forces a display beyond the number of
significant digits.   So with that, your rnorm(1) result will also have more
than the eight digits you saw earlier:
> print(rnorm(1), digits=18)
[1] -0.201840514213267291

Hope this helps,  Dirk

-- 
Hell, there are no rules here - we're trying to accomplish something. 
                                                  -- Thomas A. Edison

You can also try:

round(runif(1)*10^4)/10^4

--Brett

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch [mailto:r-help-bounces at
stat.math.ethz.ch] On Behalf Of Dirk Eddelbuettel
Sent: Thursday, April 20, 2006 8:18 PM
To: zhongmiao wang
Cc: r-help at stat.math.ethz.ch
Subject: Re: [R] how to control the data type


On 20 April 2006 at 22:00, zhongmiao wang wrote:
| Hello:
| I am generating a random number with rnorm(1). The generated number 
| has 8 decimals. I don't want so many decimals. How to control the 
| number of decimals in R?

You must have installed the professional version of R, just downgrade to the
home version which has only four digits precision.

Seriously, your equating display precision with the representation -- which is
not correct.  Consider:
> a <- 1/3
> print(a)
[1] 0.3333333
> print(a, digits=18)
[1] 0.333333333333333315

where the second print statement forces a display beyond the number of
significant digits.   So with that, your rnorm(1) result will also have more
than the eight digits you saw earlier:
> print(rnorm(1), digits=18)
[1] -0.201840514213267291

Hope this helps,  Dirk

--
Hell, there are no rules here - we're trying to accomplish something. 
                                                  -- Thomas A. Edison

______________________________________________
R-help at stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html

Have a look at  ?round for one way. 

----- Original Message ----
From: zhongmiao wang <zhongmiao at gmail.com>
To: r-help at stat.math.ethz.ch
Sent: Thursday, April 20, 2006 11:00:25 PM
Subject: [R] how to control the data type

Hello:
I am generating a random number with rnorm(1). The generated number
has 8 decimals. I don't want so many decimals. How to control the
number of decimals in R?
Thanks!

Zhongmiao Wang

______________________________________________
R-help at stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html