how to plot linear regression ?

i want to do linear regression for : log(vp)=A-B/(T+273.15) !!

vp = [    1     5    10    20    40    60   100   200   400   760]
T = [-36.7  -19.6  -11.5   -2.6   7.6   15.4   26.1 42.2   60.6   80.1]

y = log10(vp);
x = 1./(T+273.15);

% fit the polynomial
p = polyfit(x,y,1)
% p = -2035.33  8.75201
y=polyval(p,x)
plot(T,y,'or',T,vp,'b')
xlabel('T (C)')
ylabel('vp (mm Hg)')

Answer 1

[Star Strider]

Try this:

figure
plot(T,vp,'or',T,10.^y,'b')
xlabel('T (C)')
ylabel('vp (mm Hg)')

The rest of the code is unchanged.

[Rand Ardat]

thank you!

[Star Strider]

As always, my pleasure!

Answer 2

[the cyclist]

You should plot

plot(T,10.^y,'or',T,vp,'b')

because you did the regression on log10(y), not y itself.

vp = [    1     5    10    20    40    60   100   200   400   760]
T = [-36.7  -19.6  -11.5   -2.6   7.6   15.4   26.1 42.2   60.6   80.1]
y = log10(vp);
x = 1./(T+273.15);
% fit the polynomial
p = polyfit(x,y,1)
% p = -2035.33  8.75201
y=polyval(p,x)
plot(T,10.^y,'or',T,vp,'b')
xlabel('T (C)')
ylabel('vp (mm Hg)')

Also, it looks like you plotted the data as a line, and the fit as individual circles. I expect you want the opposite, which is more conventional.

[Rand Ardat]

thank you