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Re: problems with the function: analyse particles

Posted by Jan Eglinger on Aug 30, 2012; 9:00am
URL: http://imagej.273.s1.nabble.com/problems-with-the-function-analyse-particles-tp4999891p4999902.html

Hi Christian and Kathrin,

the Area fraction is determined as the percentage of area above
threshold within the current ROI (or the entire image if no selection is
active). I guess that's the reason why 'analyse particles' shows 100%
area fraction for each particle, because each particle is a single ROI,
and 100% of that particle are above threshold.

Jan



On 30.08.2012 10:27 AM, Christian Goosmann wrote:

> Hi Kathrin,
> hey, you got me surprised. The area fraction shows 100% for each
> particle also when I try it with the blob sample from the ImageJ file
> menu. It seems also to be dependent on the scaling set in 'Analyze>set
> scale...' . Maybe one of the programmers know why the area fraction is
> not expressed as fraction of the whole image which would be what I'd
> expect. For the time being a workaround for you is to get the total area
> of your frame from the image information or by selecting the whole image
> (ctl+a) and making a measurement (ctl+m). With this figure you can
> calculate each fraction of a particle in an excel  or calc -table.
> By the way, have you noticed that the results menu in the results window
> can show you a histogram of the distribution in your measurements? Maybe
> that is also useful for you.
> Good luck
> Christian
>
> Kathrin Kolotzek wrote:
>> Hey Christian, Hey Larry
>>
>> thanks for your quick respons.
>>
>> We are having an alloy which is pressed out of grains. And depending
>> the parameters there are sometimes more and bigger pores and sometimes
>> not. So  I want to determine the  porosity depending the used parameters.
>> Furthermore I am interested in the percentage area of the particles
>> to sort them better out.
>>
>> Christian I think u mean something like this here: (I shortend it and
>> just listets area and %area) right?
>>
>>     Area       %area
>> 1    12        100
>> 2    12        100
>> 3    12        100
>> 4    446       100
>> 5    12        100
>>
>>
>> And here I was wondering why it always says 100% in %area, no matter
>> what size the particle has.
>> So do I have this right, in your opinion I should just take the values
>> which are presented in the gap "area" and calculate the %area on my own?
>>
>> Thanks in regard.
>> Kathrin
>>
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>>
>
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