Re: [R] How is the relation between Frequency and Counts in hist/density defined?

From: Bert Gunter <gunter.berton_at_gene.com>
Date: Mon, 23 May 2011 08:16:53 -0700

... Which makes the cumulative (discrete) distribution 1, as it should be.

On Mon, May 23, 2011 at 7:59 AM, Tal Galili <tal.galili_at_gmail.com> wrote:
> Thanks Richard!
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> On Mon, May 23, 2011 at 5:56 PM, <Richard.Cotton_at_hsl.gov.uk> wrote:
>
>>
>> > In order to do this I can use the relation between count and density, but
>> I
>> > would like to know if there is a way for me to predict it upfront.
>>
>> In the code for hist.default, you'll see the line
>>
>> dens <- counts/(n * diff(breaks))
>>
>> > Here is an example:
>> >
>> > set.seed(242)
>> > z = rnorm(30)
>> > hist_z <- hist(z)
>> > hist_z$counts / hist_z$density # the relation is 15
>>
>> In your example, n is 30, and the breaks are evenly spaced every 0.5.
>>
>> Regards,
>> Richie.
>>
>> Mathematical Sciences Unit*
>> **HSL* <http://www.hsl.gov.uk/contact-us.htm>*
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-- 
"Men by nature long to get on to the ultimate truths, and will often
be impatient with elementary studies or fight shy of them. If it were
possible to reach the ultimate truths without the elementary studies
usually prefixed to them, these would not be preparatory studies but
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-- Maimonides (1135-1204)

Bert Gunter
Genentech Nonclinical Biostatistics

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Received on Mon 23 May 2011 - 15:19:23 GMT

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