Re: fixed bin width

From: Adrian Sevcenco <Adrian.Sevcenco_at_cern.ch>
Date: Tue, 8 Jul 2008 17:43:34 +0300


Rene Brun wrote:
> Although your request could be implemented, it would have several
> side-effects in reality,
> the main one being possible memory overflows because to accommodate a
> large under/overflow many bins could be required.
> Did you experience any problem with the existing automatic binning? Note
> that with the auto binning algorithm nice values are computed for the
> bin width and also the origin. And it is teh algorithm used by
> TTree::Draw too.
>
> Rene Brun

No, i didn't have any problems with automatic binning. I was asking for this because in the case of automatic binning the bins are enlarged. "The used method is to double the bin size until the new value fits in the range, merging bins two by two" Root guide 5.16 Automatic Re-binning Option.
I was looking for an easier way than using trees for filling a histogram

   with a bin width that is not modified no matter what. For example in CAF if i parse a lot of events and i fill a histogram with a single value for a given event i cannot be sure that the final merged histogram will keep the initial bin width.
So .. i will use a tree :)
Thanks for answers and patience,
Best regards,
Adrian

> Adrian Sevcenco wrote:

>> Rene Brun wrote:
>>> Yes, use automatic binning
>>>  TH1F *h = new TH1F("h","title",100,0,0);
>> Thanks for the answer. but ... wouldn't this give me
>> an histogram with a fixed number of bins ? that will have their widths
>> increased as it is filled?
>> In principle i was asking about something that will scale the axis 
>> range (and number of bins) without modifying the bin width.
>> I ask about this because i would like to have a histogram on which i 
>> only declare the bin width and that afterwards grow (axis and number 
>> of bins) as i fill it.
>> Thank you,
>> Best regards,
>> Adrian
>>
>>> Setting the upper limit <= lower limit will trigger the automatic 
>>> binning (true for 1,2 and 3 dimensions)
>>>
>>> Rene Brun
>>>
>>> Adrian Sevcenco wrote:
>>>> Hi,
>>>> Is there a possibility of setting up a histogram with a fixed bin 
>>>> width that will keep scaling the axis range automatically as it is 
>>>> filled?
>>>> Thank you,
>>>> Best regards,
>>>> Adrian
>>

>

Received on Tue Jul 08 2008 - 16:43:58 CEST

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