Make polyfit instead of plot

Hi,

id like to make this into a polyfit instead of a plot.

% Plotting of FRF
fig = figure(1000+p);p=p+1;
set(fig, 'WindowStyle', 'docked');
set(gcf,'color','w');
subplot(3,1,1);
if HOLD
    hold on;
end

plot(f,abs(FRF), color, 'linewidth', 2);
ylim([0 1.5]);
xlim([0,f_range]);
grid on;box on;
ylabel('Speed/Speed*');

[Geoff Hayes]

@Zakir Mahmood - does it make sense to use polyfit? What would n be?

[rockstar49]

hey im not sure what n would be in this case.

[dpb]

What in the world is FRF??? Does the plot bear any relationship to a polynomial of some degree?

With zero useful information, pretty-much at a loss here...

[Star Strider]

@Zakir Mahmood — What result do you want?

@dpb — Probably: Frequency Response Function.

Answer 1

[Walter Roberson]

polynomial_degree = 3;  %adjust as appropriate

p = polyfit(f, abs(FRF), polynomial_degree);

fig = figure(1000+p);p=p+1;
set(fig, 'WindowStyle', 'docked');
set(gcf,'color','w');
subplot(3,1,1);
if HOLD
    hold on;
end

plot(f,abs(FRF), color, 'linewidth', 2, 'DisplayName', 'abs(FRF)');

y = polyval(p, f);
oldhold = hold('on');
plot(f, y, 'b', 'Linewidth', 2, 'DisplayName', 'fitted abs(FRF)');
hold(oldhold)

ylim([0 1.5]);
xlim([0,f_range]);
grid on;box on;
ylabel('Speed/Speed*');
legend show