help with regression fitting - curvilinear

I lost on why the model cant plot a single line after fitting a regression to the data (example data attached).

I'm using,

p = polyfit(data(:,2), data:,1), 2); 
ypoly = poly val(p, data(:,2));

figure
plot(data(:,2), data(:,1), 'o')
hold on
plot(data(:,2), ypoly)

The figure looks like this (attached) with lines all over instead of one smooth curve.

Answer 1

[KSSV]

load('data.mat')
p = polyfit(data(:,2), data(:,1), 2); 
xi = linspace(min(data(:,1)),max(data(:,2)),1000) ; 
yi = polyval(p, xi);

figure
plot(data(:,2), data(:,1), 'o')
hold on
plot(xi,yi)

You made some syntax errors in the given code. Check with the given code.

[Eric Escoto]

Thanks!