R help - Jul 2012 - Histogram

I have a column of 1000 datapoints from the normal distribution with mean 2
and variance 4. How can I get a histogram of these observations with 20
bins with each bin having 50 observations?

-- 
Thanks,
Jim.

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Hi Jim,

You can't specify both number of bins and bin size. You can specify
breaks: either the number of bins or the location of breakpoints. A
histogram with 20 bins of 50 observations each must by definition come
from a uniform distribution.

What are you trying to accomplish?

Sarah

On Thu, Jul 5, 2012 at 3:29 PM, Jim Silverton <jim.silverton at gmail.com>
wrote:
> I have a column of 1000 datapoints from the normal distribution with mean 2
> and variance 4. How can I get a histogram of these observations with 20
> bins with each bin having 50 observations?
>
> --
> Thanks,
> Jim.

-- 
Sarah Goslee
http://www.functionaldiversity.org

Hello,

Try the following.

x <- rnorm(1000, mean=2, sd=2)
p <- seq(0, 1, by=1/20)
quant <- quantile(x, probs=p)
hist(x, breaks=quant)


The method is absolutely general, that's why I've separated the several 
steps, to make it clear.

Hope this helps,

Rui Barradas

Em 05-07-2012 20:29, Jim Silverton escreveu:
> I have a column of 1000 datapoints from the normal distribution with mean 2
> and variance 4. How can I get a histogram of these observations with 20
> bins with each bin having 50 observations?
>

There's no reason you can't do that with normally-distributed data,
though I'm not sure why you'd want to. My point was rather that you
can't specify the bin width and size both. If you let the bin size
vary, this will work:

set.seed(1234)
mydata <- rnorm(1000, mean = 2, sd = 4)
mydata.hist <- hist(mydata, breaks=quantile(mydata, probs=seq(0, 1,
length.out = length(mydata)/50 + 1)))
mydata.hist$counts


Sarah

On Thu, Jul 5, 2012 at 3:37 PM, Jim Silverton <jim.silverton at gmail.com>
wrote:
> Thanks Sarah!!
> Ok so if I have say x = runif(1000,0,1) say instead if the normal and I
want
> a histogram with bins that have an equal number of observations. For
example
> if I want each bin to have 50 observations, how do I do this?
>
>
>
> On Thu, Jul 5, 2012 at 3:34 PM, Sarah Goslee <sarah.goslee at
gmail.com> wrote:
>>
>> Hi Jim,
>>
>> You can't specify both number of bins and bin size. You can specify
>> breaks: either the number of bins or the location of breakpoints. A
>> histogram with 20 bins of 50 observations each must by definition come
>> from a uniform distribution.
>>
>> What are you trying to accomplish?
>>
>> Sarah
>>
>> On Thu, Jul 5, 2012 at 3:29 PM, Jim Silverton <jim.silverton at
gmail.com>
>> wrote:
>> > I have a column of 1000 datapoints from the normal distribution
with
>> > mean 2
>> > and variance 4. How can I get a histogram of these observations
with 20
>> > bins with each bin having 50 observations?
>> >
>> > --
>> > Thanks,
>> > Jim.
>>
-- 
Sarah Goslee
http://www.functionaldiversity.org