Confused by output from Polyval











up vote
1
down vote

favorite












I have some data from which I have fitted a 2nd order polynomial using numpy.polynomial.polynomial.polyfit



data_fit = poly.polyfit(length_spline_a, temp_spline_b, 2)


I am examining changes in length, and have a list of 10% changes in length



len_steps = 0.0, -0.012573565669572757, -0.025147131339145513, -0.03772069700871827...

print (len(len_steps)

>>>>11


My assumption was that polyval would solve for y for each of the x values in the len_steps list



y_data = poly.polyval(data_fit, len_steps)


However this provides a list with only 3 data points rather than the 11 I expected. 



print(y_data)

>>>>[-5.34112443e+21 -2.50395581e+28 -6.75169134e+28]


Have I mis understood the purpose of polyval or have I done something wrong?






python python-3.x numpy polynomials







share|improve this question




























    up vote
    1
    down vote

    favorite












    I have some data from which I have fitted a 2nd order polynomial using numpy.polynomial.polynomial.polyfit



    data_fit = poly.polyfit(length_spline_a, temp_spline_b, 2)


    I am examining changes in length, and have a list of 10% changes in length



    len_steps = 0.0, -0.012573565669572757, -0.025147131339145513, -0.03772069700871827...
    
print (len(len_steps)
    
>>>>11


    My assumption was that polyval would solve for y for each of the x values in the len_steps list



    y_data = poly.polyval(data_fit, len_steps)


    However this provides a list with only 3 data points rather than the 11 I expected. 



    print(y_data)
    
>>>>[-5.34112443e+21 -2.50395581e+28 -6.75169134e+28]


    Have I mis understood the purpose of polyval or have I done something wrong?






    python python-3.x numpy polynomials







    share|improve this question


























      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      I have some data from which I have fitted a 2nd order polynomial using numpy.polynomial.polynomial.polyfit



      data_fit = poly.polyfit(length_spline_a, temp_spline_b, 2)


      I am examining changes in length, and have a list of 10% changes in length



      len_steps = 0.0, -0.012573565669572757, -0.025147131339145513, -0.03772069700871827...
      
print (len(len_steps)
      
>>>>11


      My assumption was that polyval would solve for y for each of the x values in the len_steps list



      y_data = poly.polyval(data_fit, len_steps)


      However this provides a list with only 3 data points rather than the 11 I expected. 



      print(y_data)
      
>>>>[-5.34112443e+21 -2.50395581e+28 -6.75169134e+28]


      Have I mis understood the purpose of polyval or have I done something wrong?






      python python-3.x numpy polynomials







      share|improve this question















      I have some data from which I have fitted a 2nd order polynomial using numpy.polynomial.polynomial.polyfit



      data_fit = poly.polyfit(length_spline_a, temp_spline_b, 2)


      I am examining changes in length, and have a list of 10% changes in length



      len_steps = 0.0, -0.012573565669572757, -0.025147131339145513, -0.03772069700871827...
      
print (len(len_steps)
      
>>>>11


      My assumption was that polyval would solve for y for each of the x values in the len_steps list



      y_data = poly.polyval(data_fit, len_steps)


      However this provides a list with only 3 data points rather than the 11 I expected. 



      print(y_data)
      
>>>>[-5.34112443e+21 -2.50395581e+28 -6.75169134e+28]


      Have I mis understood the purpose of polyval or have I done something wrong?






      python python-3.x numpy polynomials




      python python-3.x numpy polynomials






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Nov 8 at 11:16

























      asked Nov 8 at 10:46









      nick.sculthorpe

      507




      507
























          1 Answer
          1






          active

          oldest

          votes

















          up vote
          0
          down vote













          The output works if I reverse the list order to y_data = poly.polyval(len_steps, data_fit) which is actually clear now I re-read the documents. I think I was using the np.polyval syntax which expects the coefs first.






          share|improve this answer





















            Your Answer






            StackExchange.ifUsing("editor", function () {
            StackExchange.using("externalEditor", function () {
            StackExchange.using("snippets", function () {
            StackExchange.snippets.init();
            });
            });
            }, "code-snippets");

            StackExchange.ready(function() {
            var channelOptions = {
            tags: "".split(" "),
            id: "1"
            };
            initTagRenderer("".split(" "), "".split(" "), channelOptions);

            StackExchange.using("externalEditor", function() {
            // Have to fire editor after snippets, if snippets enabled
            if (StackExchange.settings.snippets.snippetsEnabled) {
            StackExchange.using("snippets", function() {
            createEditor();
            });
            }
            else {
            createEditor();
            }
            });

            function createEditor() {
            StackExchange.prepareEditor({
            heartbeatType: 'answer',
            convertImagesToLinks: true,
            noModals: true,
            showLowRepImageUploadWarning: true,
            reputationToPostImages: 10,
            bindNavPrevention: true,
            postfix: "",
            imageUploader: {
            brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
            contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
            allowUrls: true
            },
            onDemand: true,
            discardSelector: ".discard-answer"
            ,immediatelyShowMarkdownHelp:true
            });


            }
            });














             

            draft saved


            draft discarded


















            StackExchange.ready(
            function () {
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53206124%2fconfused-by-output-from-polyval%23new-answer', 'question_page');
            }
            );

            Post as a guest















            Required, but never shown

























            1 Answer
            1






            active

            oldest

            votes








            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            0
            down vote













            The output works if I reverse the list order to y_data = poly.polyval(len_steps, data_fit) which is actually clear now I re-read the documents. I think I was using the np.polyval syntax which expects the coefs first.






            share|improve this answer

























              up vote
              0
              down vote













              The output works if I reverse the list order to y_data = poly.polyval(len_steps, data_fit) which is actually clear now I re-read the documents. I think I was using the np.polyval syntax which expects the coefs first.






              share|improve this answer























                up vote
                0
                down vote










                up vote
                0
                down vote









                The output works if I reverse the list order to y_data = poly.polyval(len_steps, data_fit) which is actually clear now I re-read the documents. I think I was using the np.polyval syntax which expects the coefs first.






                share|improve this answer












                The output works if I reverse the list order to y_data = poly.polyval(len_steps, data_fit) which is actually clear now I re-read the documents. I think I was using the np.polyval syntax which expects the coefs first.







                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered Nov 8 at 11:26









                nick.sculthorpe

                507




                507






























                     

                    draft saved


                    draft discarded



















































                     


                    draft saved


                    draft discarded














                    StackExchange.ready(
                    function () {
                    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53206124%2fconfused-by-output-from-polyval%23new-answer', 'question_page');
                    }
                    );

                    Post as a guest















                    Required, but never shown





















































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown

































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown







                    -

                    Popular posts from this blog

                    Guess what letter conforming each word

                    Image
                    6 $begingroup$ This is an entry in the Fortnightly Topic Challenge #41: Short and Sweet. 1 letter only could be mean anything . With an additional letter in front , could be used as medicine component and something you definitely learn or at least heard once. Add another letter in front , you would possibly hear that many times . Add an additional letter in front , you would found an independent country . With an additional letter, in the end , you would found something related to apple . Add another letter in the end , you would found something bad . Hint: Each letter is unique . word knowledge letters chemistry share | improve this question ...
                    Read more

                    Port of Spain

                    Image
                    For ports in the country of Spain, see List of ports in Spain. City in City of Port of Spain, Trinidad and Tobago Port of Spain City City of Port of Spain Top to bottom (left to right): Skyline of Port of Spain from Gulf of Paria; National Academy for the Performing Arts, Independence Square, Eric Williams Plaza; MovieTowne, Port of Port of Spain Motto(s):  "We Gather Strength As We Go Along" Port of Spain Coordinates: 10°40′N 61°31′W  /  10.667°N 61.517°W  / 10.667; -61.517 Coordinates: 10°40′N 61°31′W  /  10.667°N 61.517°W  / 10.667; -61.517 Country   Trinidad and Tobago Jurisdiction City of Port of Spain Settled 1560 Incorporated (town) 1853 Incorporated (city) 1914 Government  • Mayor Joel Martinez  • Governing body City Corporation Area [1]  • City 12 km 2 (5 sq mi) Elevation [2] 66 m (217 ft) Population (2011) [1]  • City 37,074  • Rank 3rd  • Density 3,090/km 2 (8,000/sq mi)...
                    Read more

                    Run scheduled task as local user group (not BUILTIN)

                    Image
                    0 I am trying to run a scheduled task with User Group (not a single user). This is working fine when I in the field "when running a task, use the following user account:" insert BUILTIN User Group (for example: Administrators or Users). But when I try it with the created Local User Group (example: TestGroup) it is not working. The Users in the TestGroup are the same as in the Administrators group. What could be the problem? Are there some restrictions to the Created User Group compared to BUILTINUsers? scheduled-tasks taskscheduler windowstaskschedule share | improve this question asked Nov 15 '18 at 15:36 Far...
                    Read more