How can I include an equation in a scatter plot with linear regression line?

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Shannon
Shannon on 24 Feb 2013
Hi,
I'm trying to add the equation for a linear regression line to a scatter plot that I have made. I first plotted my data points then used the polyfit function to add a first-order line to my plot. Now I want the equation of the line in y = mx + b form to appear on my scatter plot, and I want the equation to update as I change my data points. Is there a command to help me do this?
Here's my code for adding the line:
%Find the best fit line for this data
bestfit = polyfit(Year,disp_pr_s,1);
disp_pr_s = bestfit(1)*Year + bestfit(2);
hold on
plot(Year,disp_pr_s,'k')
hold off
Thanks in advance!

Accepted Answer

Image Analyst
Image Analyst on 24 Feb 2013
Use sprintf() to build a string. Then use text() to place it
theString = sprintf('y = %.3f x + %.3f', bestfit(1), bestfit(2));
text(x, y, theString, 'FontSize', 24);
  1 Comment
Shannon
Shannon on 24 Feb 2013
Great, I got this to work as soon as I realized that x and y in "text(x, y, theString, 'FontSize', 24)" refer to actual coordinates dependent on my x and y axis in the original plot.
Thanks!

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