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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

I have histogram shown in this figure : http://i1069.photobucket.com/albums/u472/tina12354/h1_zps40094c32.png

The problem is i need to detect peaks and valleys .

i tested 1st derivative . and where if difference tend to 0. there is a valley .

but for example if upper slope have value 26 , 26 . then it will also tend to 0. which will hard to tell that its valley or peak.

Any idea to get peak and valleys .

thanks

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,727

Hi tina123;

That histogram is for discrete values. Using derivatives is for continuous data. You generally can not find peaks and valleys of discrete dat using derivatives.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

Then Is there any way to find peaks and valley s?

Please guide me in this regard .

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,727

You could search through the discrete data for maximum values and minimum values.

Below is a histogram for this data

You can get the peak by just counting how many of each type of numbers there are. There are 4 ones, this is the most.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

so you meant the minimum value would be our valley . is it ?

In your data set .. 1 is the most minimum value .

so it would be a valley . Is it ?

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,727

A histogram charts occurences. One has 4 occurences as you see in the histogram. It is a peak not a valley.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

bobbym wrote:

A histogram charts occurences. One has 4 occurences as you see in the histogram. It is a peak not a valley.

ok and now about the valley ?

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,727

Hi;

Look at the histogram. 2 is a valley because there is only one of them. 3 is a valley because there is only one of them. 7 i s a valley. Can you find more.

This is only way one of looking at this data if I understand you correctly.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

So i think check occurrence of each data .. valley will be there where occurrence would be minimum,

and maximum occurrence would be peak .

but for example if 1 is repeated 4 time 10 is repeated 3 . then we would have two peaks at 1 having 4 occurence and 10 having 3 occurrence . and say 5 have occurrence 2 .. so minimum occurence would be our valley .

right ?

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**anonimnystefy****Real Member**- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,015

Hi tina123

What exactly would you consider peaks and valleys in the picture in your first post?

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,727

Hi tina123;

Yes, minimum occurence would be a valley. There could be more than one.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

anonimnystefy wrote:

Hi tina123

What exactly would you consider peaks and valleys in the picture in your first post?

Well if we consider only useful data . then its from i = 0 ; i < 46 ; i++ , get minimum value. it would be 2 . which will be our valley . but for and 21 will be our maxmum peak .

that 's by considering minimum and maximum histogram value .

But i still not understand correctly

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,727

Hi;

Want to see another example?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

bobbym wrote:

Hi tina123;

Yes, minimum occurence would be a valley. There could be more than one.

Hy Bobvym , I am confused . Could u tell me peaks and valleys in the same theory that u recently explained .

thanks .

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

bobbym wrote:

Hi;

Want to see another example?

Well i understand with an example that recently u mentioned .

but i did not get valley and peak in my #1 post .

Could you please make my mind clear from histogram of post #1 .

thanks

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,727

Here is a histogram like yours, it contains values from 0 to 46.

Can you find the valley?

Could you please make my mind clear from histogram of post #1 .

thanks

That I cannot do. That drawing is not labelled so how can tell what the peaks are? I can pick them out but I do not know what numbers they are. Also I do not have the data and I can not get from that picture.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

well in my #1 post ,

on axis .. we have index 0 to 53

and on y axis ,. we have , 0 to 21 .

like on axis 0 will have bar 19 length .. like that

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,727

You say that on the x axis we go from 0 to 53. Does that mean the whole black area or just the red?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

bobbym wrote:

You say that on the x axis we go from 0 to 53. Does that mean the whole black area or just the red?

Well all bins are in red color .

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,727

I can not see bins it it too small.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

bobbym wrote:

I can not see bins it it too small.

Well actually i maked histogram in range 0 to 180 . and to make histogram i consider bins 180 . so bins size is so small .

and after removing some noise and part of histogram .

i got the histogram that i posted in #p1 ..

so now our left bins are in range 0 to 53 .

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,727

I have marked off two peaks, I can not see what number they are.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

bobbym wrote:

I have marked off two peaks, I can not see what number they are.

oh i gave histogram values too with its horizontal axis .

2nd peak value is 21 . and 1st peak value is 20 .

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,727

Do you see what a peak is?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**tina123****Member**- Registered: 2012-04-29
- Posts: 83

bobbym wrote:

Do you see what a peak is?

as i understand peak is maximum value .. and 20 , 21 are the maximum . .

so those are peaks

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