How can I automate the fplot of a polynomial as a function of its degree?

Hi everybody,

I have the following part of a script, in which I plot a polynomial function obtained thorugh a polyfit on measured data.

The script works well, but I was wondering how to automate it as a dunction of the value of g (polynomal degree), without manually changing the f equation.

Thank you very much!

load=[0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0];%measured data 
efficiency=[0.274766154 0.567610421 0.700286086 0.766121699 0.831135824 0.848797812...
    0.868255235 0.881644769 0.892014 0.898709 0.9018];%measured data 

g=5;%polynomial degree

p=polyfit(load,efficiency,g);%coefficient calculation


f=@(x) p(1)*(x)^5+p(2)*(x)^4+p(3)*(x)^3+p(4)*(x)^2+p(5)*(x)+p(6); %polynomial function

figure1=figure('color','w','Position',[1,41,1000,500],'Renderer', 'Painters');
fplot(f,[0 0.9],'linewidth', 1.5,'color',[0.8500, 0.3250, 0.0980]);%plot

Answer 1

[KSSV]

Why you want to use fplot? You can striaght away use polyval.

load=[0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0];%measured data 
efficiency=[0.274766154 0.567610421 0.700286086 0.766121699 0.831135824 0.848797812...
    0.868255235 0.881644769 0.892014 0.898709 0.9018];%measured data 

g=5;%polynomial degree

p=polyfit(load,efficiency,g);%coefficient calculation

x = linspace(0,0.9,20) ;
y = polyval(p,x,'*r') ; 

f=@(x) p(1)*(x)^5+p(2)*(x)^4+p(3)*(x)^3+p(4)*(x)^2+p(5)*(x)+p(6); %polynomial function

figure1=figure('color','w','Position',[1,41,1000,500],'Renderer', 'Painters');
fplot(f,[0 0.9],'linewidth', 1.5,'color',[0.8500, 0.3250, 0.0980]);%plot

Warning: Function behaves unexpectedly on array inputs. To improve performance, properly vectorize your function to return an output with the same size and shape as the input arguments.

hold on
plot(x,y,'sb')

If you are supposed to use polynomial then you can achieve that using poly2sym. Read about this function.

[Andrea Costantino]

Definitively better with polyval . Thank you so much!