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JohnRudnicki15-Moonstone
15-Moonstone
June 10, 2020
Solved

Maxima and Minima

  • June 10, 2020
  • 5 replies
  • 4054 views

I have a series of plots similar to the one below with multiple peaks and troughs. I want to get the values of the peaks and troughs and their x coordinate. The only way I can think to do it is to use max to find the value of the biggest peak, remove that section of data, find the next and so on. This is tedious and I have many to do. There must be a better way. Can someone show me what it is. Worksheet is attached. 

 

JohnRudnicki_0-1591814111040.png

 

Best answer by terryhendicott

HI,

 

If you do not have the data extension pack you can resolve the minimum and maximum.

 

Sheet is enclosed.

 

Regards

Terry

5 replies

V
24-Ruby IV
ValeryOchkov24-Ruby IV
24-Ruby IV
June 10, 2020

mn.png

mx.png

J
JohnRudnicki15-MoonstoneAuthor
15-Moonstone
June 10, 2020

Thanks for your reply, Valery. Probably my question was not clear. In addition to the value and position of the highest peak (and lowest trough), I want to get the maximum and minimum values of all the peaks and troughs (i.e., four of each in the example shown). 

M
mvenich14-Alexandrite
14-Alexandrite
June 10, 2020

The better way is to use the FindPeaks function in Maple or the findpeaks function in Matlab.

Nothing in Mathcad will help you do that easily.

D
DJF16-Pearl
16-Pearl
June 10, 2020

Well, the slope changes sign at each max or min.  So if you calculate local slopes or derivatives you could step through and look for sign changes.  This wouldn't work well with noisy data, but if your data is well behaved you might get ok results.

W
Werner_E25-Diamond I
25-Diamond I
June 11, 2020

 How about using Mathcads "localmax" function (from Data Analysis Extension Pack)?

Werner_E_3-1591841362898.png

 

 

 

 

    J
    JohnRudnicki15-MoonstoneAuthor
    15-Moonstone
    June 11, 2020

    Nice. Unfortunately, I do not have the Data Analysis Extension Pack.

    W
    Werner_E25-Diamond I
    25-Diamond I
    June 11, 2020
    @JohnRudnicki wrote:

    Nice. Unfortunately, I do not have the Data Analysis Extension Pack.

    As far as I know the DAEP is part of every Mathcad distribution since MC14, apart from some single user edu licences, where the pack and its help is also installed during installation but the license for it is missing. In Prime its integrated anyway. Did you give it a try?

    But in case you are using an older version of MC (from the pic you posted it looked like MC14 or MC15 anyway) or have a version without a license for the DAEP, its not hard to recode those functions. You will find examples how to do here in the forum, as an example

    https://community.ptc.com/t5/PTC-Mathcad/Improve-localmax-results/m-p/546078/highlight/true#M179863

    or

    https://community.ptc.com/t5/PTC-Mathcad/Gaussian-fit-to-several-peaks/m-p/147888/highlight/true#M58106

     

    T
    21-Topaz II
    terryhendicott21-Topaz IIAnswer
    21-Topaz II
    June 11, 2020

    HI,

     

    If you do not have the data extension pack you can resolve the minimum and maximum.

     

    Sheet is enclosed.

     

    Regards

    Terry

      J
      JohnRudnicki15-MoonstoneAuthor
      15-Moonstone
      June 11, 2020

      Clever. Thanks.

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