# Fit a line to data using regress

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Nicholas Deosaran on 25 Sep 2020
Edited: Adam Danz on 28 Sep 2020
Hey all, I am trying to use a new matlab function "regress" and would like some help on how to use it to fit a line.
below is my code that I have so far, but lost on how to use the "regress" function.
x = 0:0.1:10;
n = 0;
noise = n*rand(1,length(x));
y = 2*x+1+noise;
figure(1);
plot(x,y,'d')

Adam Danz on 25 Sep 2020
Edited: Adam Danz on 25 Sep 2020

Nicholas Deosaran on 25 Sep 2020
Oh okay, I see.
and to plot that line on the axis..will it be
x = 0:0.1:10;
n = 0;
noise = n*rand(1,length(x));
y = 2*x+1+noise;
b = regress(y(:),x(:));
plot(x,y,'d') %plot as diamonds
hold on
plot(b,y)
hold off
is that correct?
Adam Danz on 25 Sep 2020
No, b is just the slope if you've used the syntax from my answer.
If you want to plot the regression line you'll need the y-intercept term. To get the y-intercept term you need to add a column of 1s to x.
b = regress(y(:),[ones(size(x(:))),x(:)]);
b is a 2x1 vector containing the [intercept; slope];
Use refline(b(2),b(1)) to add the regression line.
Or, check out lsline.
Or, check out polyfit(x,y,1) along with refline.