Math Is Fun Forum / detect peaks and valleys

tina123 · 2012-09-21 21:54:51

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

bobbym · 2012-09-21 22:11:25

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.

tina123 · 2012-09-21 22:14:37

Then Is there any way to find peaks and valley s?
Please guide me in this regard .

bobbym · 2012-09-21 22:18:44

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.

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tina123 · 2012-09-22 23:06:59

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 ?

bobbym · 2012-09-22 23:08:19

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

tina123 · 2012-09-22 23:09:46

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 ?

bobbym · 2012-09-22 23:13:50

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.

tina123 · 2012-09-22 23:14:15

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 ?

anonimnystefy · 2012-09-22 23:18:04

Hi tina123

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

bobbym · 2012-09-22 23:21:36

Hi tina123;

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

tina123 · 2012-09-22 23:30:22

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

bobbym · 2012-09-22 23:31:18

Hi;

Want to see another example?

tina123 · 2012-09-22 23:34:39

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 .

tina123 · 2012-09-22 23:36:33

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

bobbym · 2012-09-22 23:42:23

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.

Uploaded Images

tina123 · 2012-09-22 23:58:27

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

bobbym · 2012-09-23 00:00:37

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

tina123 · 2012-09-23 00:03:11

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 .

bobbym · 2012-09-23 00:12:16

I can not see bins it it too small.

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tina123 · 2012-09-23 00:17:47

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 .

bobbym · 2012-09-23 00:18:52

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

tina123 · 2012-09-23 00:23:36

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 .

bobbym · 2012-09-23 00:33:17

Do you see what a peak is?

tina123 · 2012-09-23 00:37:55

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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#1 2012-09-21 21:54:51

detect peaks and valleys

#2 2012-09-21 22:11:25

Re: detect peaks and valleys

#3 2012-09-21 22:14:37

Re: detect peaks and valleys

#4 2012-09-21 22:18:44

Re: detect peaks and valleys

#5 2012-09-22 23:06:59

Re: detect peaks and valleys

#6 2012-09-22 23:08:19

Re: detect peaks and valleys

#7 2012-09-22 23:09:46

Re: detect peaks and valleys

bobbym wrote:

#8 2012-09-22 23:13:50

Re: detect peaks and valleys

#9 2012-09-22 23:14:15

Re: detect peaks and valleys

#10 2012-09-22 23:18:04

Re: detect peaks and valleys

#11 2012-09-22 23:21:36

Re: detect peaks and valleys

#12 2012-09-22 23:30:22

Re: detect peaks and valleys

anonimnystefy wrote:

#13 2012-09-22 23:31:18

Re: detect peaks and valleys

#14 2012-09-22 23:34:39

Re: detect peaks and valleys

bobbym wrote:

#15 2012-09-22 23:36:33

Re: detect peaks and valleys

bobbym wrote:

#16 2012-09-22 23:42:23

Re: detect peaks and valleys

#17 2012-09-22 23:58:27

Re: detect peaks and valleys

#18 2012-09-23 00:00:37

Re: detect peaks and valleys

#19 2012-09-23 00:03:11

Re: detect peaks and valleys

bobbym wrote:

#20 2012-09-23 00:12:16

Re: detect peaks and valleys

#21 2012-09-23 00:17:47

Re: detect peaks and valleys

bobbym wrote:

#22 2012-09-23 00:18:52

Re: detect peaks and valleys

#23 2012-09-23 00:23:36

Re: detect peaks and valleys

bobbym wrote:

#24 2012-09-23 00:33:17

Re: detect peaks and valleys

#25 2012-09-23 00:37:55

Re: detect peaks and valleys

bobbym wrote:

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