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#165 Singular matrix in Invert RtR error during fit

open
nobody
None
5
2014-03-08
2014-03-07
Carla
No

I'm having a problem during fit my data.
I have data for x,y,z and I want find a good correlation for z as a function of x and y. From the data vizualization I can guess that the expression will be z=-ax+by+c. I tried fit the data with this kind of expression and I obtained

"Singular matrix in Invert RtR error during fit"

If I try an expression like z=-x+y+c there are no problems with the data fitting, but the expression predict higher values and not so close to the data as expected. Then I tried adjust by hand the a,b and c parameters and I get a better approximation to the data than the previous.

Why is this happening and how can I solve it?

Related

Support Requests: #165

Discussion

  • That's impossible to answer without seeing a good deal more details of the problem. For starters: the actual data, the exact gnuplot command sequence, the version of gnuplot you're running.

     
    • Carla
      Carla
      2014-03-08

      Please find in attachment the actual data and the exact gnuplot command
      sequence tested. I'm using gnuplot version 4.6.
      I'm quite new on using gambit to fit 3D data...

      2014-03-07 21:46 GMT+01:00 Hans-Bernhard Broeker broeker@users.sf.net:

      That's impossible to answer without seeing a good deal more details of the
      problem. For starters: the actual data, the exact gnuplot command sequence,
      the version of gnuplot you're running.


      Status: open
      Group:
      Created: Fri Mar 07, 2014 11:41 AM UTC by Carla
      Last Updated: Fri Mar 07, 2014 11:41 AM UTC
      Owner: nobody

      I'm having a problem during fit my data.
      I have data for x,y,z and I want find a good correlation for z as a
      function of x and y. From the data vizualization I can guess that the
      expression will be z=-ax+by+c. I tried fit the data with this kind of
      expression and I obtained

      "Singular matrix in Invert RtR error during fit"

      If I try an expression like z=-x+y+c there are no problems with the data
      fitting, but the expression predict higher values and not so close to the
      data as expected. Then I tried adjust by hand the a,b and c parameters and
      I get a better approximation to the data than the previous.

      Why is this happening and how can I solve it?

      Sent from sourceforge.net because you indicated interest in
      https://sourceforge.net/p/gnuplot/support-requests/165/

      To unsubscribe from further messages, please visit
      https://sourceforge.net/auth/subscriptions/

       

      Related

      Support Requests: #165

      • The reason is quite simple: your commands failed to actually make a 3D fit because they lack the necessary "using" specification.

        fit f(x,y) "3DdataLinear.txt" using 1:2:3:(1.0) via a0,a1,a2
        

        would have worked.

         
        • Carla
          Carla
          2014-03-09

          It is working now. Thank you!

          2014-03-08 22:05 GMT+01:00 Hans-Bernhard Broeker broeker@users.sf.net:

          The reason is quite simple: your commands failed to actually make a 3D fit
          because they lack the necessary "using" specification.

          fit f(x,y) "3DdataLinear.txt" using 1:2:3:(1.0) via a0,a1,a2

          would have worked.

          Status: open
          Group:
          Created: Fri Mar 07, 2014 11:41 AM UTC by Carla
          Last Updated: Sat Mar 08, 2014 12:21 PM UTC
          Owner: nobody

          I'm having a problem during fit my data.
          I have data for x,y,z and I want find a good correlation for z as a
          function of x and y. From the data vizualization I can guess that the
          expression will be z=-ax+by+c. I tried fit the data with this kind of
          expression and I obtained

          "Singular matrix in Invert RtR error during fit"

          If I try an expression like z=-x+y+c there are no problems with the data
          fitting, but the expression predict higher values and not so close to the
          data as expected. Then I tried adjust by hand the a,b and c parameters and
          I get a better approximation to the data than the previous.

          Why is this happening and how can I solve it?

          Sent from sourceforge.net because you indicated interest in
          https://sourceforge.net/p/gnuplot/support-requests/165/

          To unsubscribe from further messages, please visit
          https://sourceforge.net/auth/subscriptions/

           

          Related

          Support Requests: #165

          Attachments
  • Carla
    Carla
    2014-03-08

     
    Last edit: Carla 2014-03-08