MATLAB: Does polyfit not exist in r2019b

polyfit

I cannot seem to get polyfit to work – and it seems like my copy doesn't even think it exists:

>> help polyfit
polyfit is a variable of type double.
>> doc polyfit
polyfit is a variable of type double.

Any help would be appreciated!

Best Answer

It does exist in r2019b. https://www.mathworks.com/help/matlab/ref/polyfit.html

You have a variable with the same name so Matlab no longer has access to the function until you delete the variable. clear('polyfit')

Rename the variable and the problem is solved.

Related Solutions

MATLAB: Matlab curve fitting tool automation for selection of fit with minimum sse.

You could certainly write your own function by using the gof output of the "fit" function.

Here is an example that shows you how to use the "fit" to see the Goodness of Fit of different methods. You could store the "gof" values in an array and find the max GoF.

function bestFitName = Gof_Finder( x, y )
    Fits = {'poly1', 'poly2', 'poly3', 'exp1'};
      for i=1:numel(Fits)
          [~,GoFs(i)] = fit( x, y,  Fits{i} );
      end
      [~, minIdx] = min([GoFs.sse]);
      bestFitName = Fits{minIdx};
  end

The above function will return the name of the best fit of the data x and y.

MATLAB: MapSolution broken in R2019b

Hi Matt and Walter,

Firstly Matt, many apologies that you've run into this unintended behavior. Also, many thanks to you both for looking into this and flagging it up.

What has happened here? The short answer is that mapSolution was made an internal function in R2019a and replaced with varindex. Once we made mapSolution internal, we repurposed it in R2019b leading to the internal error you encountered. We will tidy up the error and add a note in the documentation pointing you to varindex

Matt's original code works with varindex

%% Define the variables
x=optimvar('x',{'x1','x2'},'LowerBound',[-100,-200]);
y=optimvar('y',1,3,'LowerBound',[0 0 0],'UpperBound',[+300,+400,+500]);
  
%% Define some constraints
C.inequ=2*sum(y)+sum(x)<=1000;
C.equ=5*sum(x)==100;
            
           
prob=optimproblem('Constraints',C,'Objective',sum(x)+sum(y));
idx = varindex(prob);

Resulting in the output

idx = 
  struct with fields:
    x: [1 2]
    y: [3 4 5]

Also, varindex allows you to get the variable index by name, e.g.

idx = varindex(prob, 'y')

Resulting a double as the output

idx =
     3     4     5

Matt, may I ask if you were aware of varindex? Also, is there anything in mapSolution that you are relying on that varindex doesn't provide?

Thanks again for flagging this and hope varindex helps!

Cheers,

Paul

Documentation for varindex:

https://uk.mathworks.com/help/optim/ug/optim.problemdef.optimizationproblem.varindex.html

Best Answer

Related Solutions

MATLAB: Matlab curve fitting tool automation for selection of fit with minimum sse.

MATLAB: MapSolution broken in R2019b

Related Question