+ Reply to Thread
Results 1 to 12 of 12

fitting curve equation 4PL and 5PL

  1. #1
    Forum Contributor
    Join Date
    11-28-2013
    Location
    Ljubljana
    MS-Off Ver
    Office 365
    Posts
    1,054

    fitting curve equation 4PL and 5PL

    Dear Sir
    I would like to know if anyone can help to apply Four-Parameter Logistic (4PL) and Five-Parameter Logistic (5PL) in excel
    Attached Images Attached Images

  2. #2
    Forum Contributor
    Join Date
    11-28-2013
    Location
    Ljubljana
    MS-Off Ver
    Office 365
    Posts
    1,054

    Re: fitting curve equation 4PL and 5PL

    more details about equation from this site
    http://help.idbssupport.com/idbs/ser...26curagt%3Dndx

  3. #3
    Forum Expert
    Join Date
    05-05-2015
    Location
    UK
    MS-Off Ver
    Microsoft? Excel? for Microsoft 365 MSO (Version 2402 Build 16.0.17328.20068) 64-bit
    Posts
    28,007

    Re: fitting curve equation 4PL and 5PL

    Please post an Excel file (not image).

  4. #4
    Forum Contributor
    Join Date
    11-28-2013
    Location
    Ljubljana
    MS-Off Ver
    Office 365
    Posts
    1,054

    Re: fitting curve equation 4PL and 5PL

    this is the data file
    Attached Files Attached Files

  5. #5
    Forum Expert
    Join Date
    05-05-2015
    Location
    UK
    MS-Off Ver
    Microsoft? Excel? for Microsoft 365 MSO (Version 2402 Build 16.0.17328.20068) 64-bit
    Posts
    28,007

    Re: fitting curve equation 4PL and 5PL

    I am no mathematician but a very quick read of 4PL suggests you need 4 parameters so as you supplied 2 "parameters" it suggests to me (in my ignorance) you cannot use this technique.

    There are respondents to this forum who are mathematicians so hopefully they will look at your request and offer advice.

  6. #6
    Forum Guru
    Join Date
    04-13-2005
    Location
    North America
    MS-Off Ver
    2002/XP and 2007
    Posts
    15,803

    Re: fitting curve equation 4PL and 5PL

    Your file consists of 6 data points and nothing more. Here's how I would do this:

    1) Enter my "initial guesses" for the parameters of the desired form of the logistics function. The 4PL is the same as the 5PL with g=1, so I'd probably set up the 5PL and decide later whether to fix g at 1 or let it float.
    2) Enter the logistics function in an adjacent column. With the right combination of relative and absolute references, you should only need to enter the formula once, then copy it down.
    3) I almost always include a column that computes some "deviation score" for each point. An absolute difference (yestimated-ymeasured) or a relative difference (yestimated/ymeasured-1) or something.
    4) Choose an objective function (OF)-- the function you want the regression to maximize/minimize. Then enter that function into the spreadsheet. This might be the sum or product of the deviation score column or some other function. If you want the common "least squares" OF, you can use the =SUMXMY2() function: https://support.office.com/en-us/art...4-e2ecee23b299
    5) Make sure Solver is installed, then call Solver and tell it to:
    5a) Set target cell -- the cell with your OF
    5b) To a minimum or maximum (whichever choice is appropriate for your chosen OF)
    5c) By changing -- the cells where you entered the initial guesses for the parameters. Here is where you will choose whether to include g or not.
    5d) Solve.

    If you have given it reasonable first guesses, it should converge on a "best fit" of the data according to the OF you programmed in. What part of that do you get stuck on?
    Quote Originally Posted by shg
    Mathematics is the native language of the natural world. Just trying to become literate.

  7. #7
    Forum Contributor
    Join Date
    11-28-2013
    Location
    Ljubljana
    MS-Off Ver
    Office 365
    Posts
    1,054

    Re: fitting curve equation 4PL and 5PL

    Dear Mrshorty
    thanks for your concern
    but i didn't understand because im not good in statistic.
    i just want to make my own file for fitting curve like with all methods of fitting like https://mycurvefit.com/
    i already get from internet file with two methods , i didnt know if low of forum allow to upload the file or not ?

  8. #8
    Forum Guru
    Join Date
    04-13-2005
    Location
    North America
    MS-Off Ver
    2002/XP and 2007
    Posts
    15,803

    Re: fitting curve equation 4PL and 5PL

    I don't know why this forum would disallow uploading those files -- unless there is some kind of copyright or license on those files that prohibits uploading to the forum or something like that.

    You may not be good in statistics, yet, but this is how you get better. I find that a lot of programming problems need to be approached by breaking things up into smaller steps, which is what I did above. The idea is to break it up into parts that you know how to do so we can focus on the parts you need to learn. I assume almost everyone knows how to do 1 -- enter values into cells. What part or parts do you not know how to do? Do you have trouble entering the logistics function for one point (step 2)? Or are you having trouble using Solver?

  9. #9
    Forum Contributor
    Join Date
    11-28-2013
    Location
    Ljubljana
    MS-Off Ver
    Office 365
    Posts
    1,054

    Re: fitting curve equation 4PL and 5PL

    this is the model file i found on internet
    Attached Files Attached Files

  10. #10
    Forum Expert shg's Avatar
    Join Date
    06-20-2007
    Location
    The Great State of Texas
    MS-Off Ver
    2003, 2010
    Posts
    40,678

    Re: fitting curve equation 4PL and 5PL

    Use Solver to minimize the RMS error by changing the five variables:

    A
    B
    C
    D
    1
    a
    2.420179
    2
    b
    1.044576
    3
    cc
    6.732798
    4
    d
    0
    5
    g
    0.61649
    6
    RMS Err
    0.036506
    C6: {=SQRT(AVERAGE((C9:C14-B9:B14)^2))}
    7
    8
    [std]
    Reading
    9
    0
    2.417
    2.420
    C9: =d + (a - d) / (1 + (A9 / cc) ^ b) ^ g
    10
    4
    1.852
    1.825
    11
    10
    1.312
    1.372
    12
    25
    0.955
    0.904
    13
    60
    0.569
    0.557
    14
    120
    0.336
    0.368
    Entia non sunt multiplicanda sine necessitate

  11. #11
    Forum Contributor
    Join Date
    11-28-2013
    Location
    Ljubljana
    MS-Off Ver
    Office 365
    Posts
    1,054

    Re: fitting curve equation 4PL and 5PL

    Dear Shg
    how can i applied this in my sheet( from where you get value for a,b cc,d,g

  12. #12
    Forum Expert shg's Avatar
    Join Date
    06-20-2007
    Location
    The Great State of Texas
    MS-Off Ver
    2003, 2010
    Posts
    40,678

    Re: fitting curve equation 4PL and 5PL


+ Reply to Thread

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. [SOLVED] apply in equation from fitting curve automatic
    By mazan2010 in forum Excel Formulas & Functions
    Replies: 4
    Last Post: 06-07-2016, 11:37 AM
  2. Curve fitting questions
    By Joe Miller in forum Excel Charting & Pivots
    Replies: 2
    Last Post: 12-22-2014, 02:45 AM
  3. How do you change curve fitting equation formats?
    By PhilHenshaw in forum Excel General
    Replies: 5
    Last Post: 10-06-2009, 01:00 PM
  4. curve fitting
    By [email protected] in forum Excel Charting & Pivots
    Replies: 1
    Last Post: 06-03-2006, 02:10 PM
  5. curve fitting a charging capacitor type curve
    By mcgradys in forum Excel General
    Replies: 4
    Last Post: 11-15-2005, 08:50 AM
  6. [SOLVED] Best fitting curve
    By ladee_bird in forum Excel Programming / VBA / Macros
    Replies: 3
    Last Post: 09-27-2005, 09:05 AM
  7. best curve fitting
    By ladee_bird in forum Excel Charting & Pivots
    Replies: 1
    Last Post: 09-20-2005, 03:05 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts

Search Engine Friendly URLs by vBSEO 3.6.0 RC 1