Keep getting this polyfit error and don't know how to fix, error using polyfit "the first two inputs must have the name number of elements"

JobSector = app.JobSectorsInSolarDropDown.Value;
switch JobSector    
    case 'Installation & Project Development'
        hold(app.UIAxes, "off")
        plot(app.UIAxes,app.xyears,app.yipd,'ob')
        %ployfit- provies coefficients for the regression
        %equation
        IPDcoef= polyfit(app.xyears,app.yipd,1);
        %IPDcoef= [m,b]
        m= IPDcoef(1);
        b= IPDcoef(2);
        %function handle
        IPDFUNC= @(x) m*x+b;
        %regression equation
        hold(app.UIAxes,"on")
        fplot(app.UIAxes,IPDFUNC,[min(app.xyears),max(app.xyears)],'-r')
end

%error i get in command window

%Error using polyfit (line 49)

%The first two inputs must have the same number of elements.

%Error in SolarAppGG/JobSectorsInSolarDropDownValueChanged (line 57)

%IPDcoef= polyfit(app.xyears,app.ymanu,1);

%Error in %matlab.apps.AppBase>@(source,event)executeCallback(ams,app,callback,requiresEventData,ev%ent) (line 62)

% newCallback = @(source, event)executeCallback(ams, ...

%Error while evaluating DropDown PrivateValueChangedFcn.

Answer 1

[dpb]

We can't see variables app.xyears,app.yipd, but if you set a breakpoint at that line, you'll be able to look at them and you'll find they are not the same length for some reason. Why, we can't tell, but that's the problem.

Example:

c=polyfit([1:3],[1:3],1)        % two row vectors same length works

c = 1×2

1.0000 0.0000

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c=polyfit([1:3],[1:3].',1)      % two vectors same length works despite orientation different

c = 1×2

1.0000 0.0000

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c=polyfit([1:4],[1:3],1)        % two vectors different length crashes and burns...

Error using polyfit (line 49)
The first two inputs must have the same number of elements.

Figure out why you have the two different lengths at that point and fix it...

[Gabriel]

thank you i just merged years and ipd into one and got it to work like that

[dpb]

" i just merged years and ipd into one..."

Well, that doesn't seem right if

plot(app.UIAxes,app.xyears,app.yipd,'ob')

is right--that implies somewhat like the variable names do, btw--that xyears is a time variable and yipd is some dependent variable. Although it should have failed also if the two lengths aren't the same...

>> plot(1:3,rand(1,4),1)
Error using plot
Vectors must be the same length. 
>> 

And, it won't work in polyfit without an x and a y vector...and clearly using the same for both is, while it will run, pretty-much useless since it would be fitting x on x for the same two x.