MATLAB: How to plot best fit line

best linegraphplot

I have 1700 plot of data in graph. How do I plot the line of best fit? I stored the x and y data in table and the plot them. From the graph, I can see that the graph plotting is upwards. I have read other answers for this kind of question but still confused. Please help. Thank you.

x = score;
y = MOS;
scatter(x,y)
xlabel('score')
ylabel('MOS')

Best Answer

Use polyfit() and polyval():

% Get coefficients of a line fit through the data.
coefficients = polyfit(x, y, 1);
% Create a new x axis with exactly 1000 points (or whatever you want).
xFit = linspace(min(x), max(x), 1000);
% Get the estimated yFit value for each of those 1000 new x locations.
yFit = polyval(coefficients , xFit);
% Plot everything.
plot(x, y, 'b.', 'MarkerSize', 15); % Plot training data.
hold on; % Set hold on so the next plot does not blow away the one we just drew.
plot(xFit, yFit, 'r-', 'LineWidth', 2); % Plot fitted line.
grid on;

See attached for a full demo.

Related Solutions

MATLAB: Intersection of line and curve from thier points

Try this:

x_line = [7020 0];
y_line = [0 250000];
x_curve = [5620 4850 4290 3600];
y_curve = [0 100000 200000 300000];
b_line = polyfit(x_line, y_line,1);                     % Fit ‘line’
y_line2 = polyval(b_line, x_curve);                     % Evaluate ‘line’ At ‘x_curve’
x_int = interp1((y_line2-y_curve), x_curve, 0);         % X-Value At Intercept
y_int = polyval(b_line,x_int);                          % Y-Value At Intercept
figure(1)
plot(x_line, y_line)
hold on
plot(x_curve, y_curve)
plot(x_int, y_int, '+r')                                % Plot Intercept Point
hold off

MATLAB: How to add line of best fit to plot

You are not accepting the coefficients from polyfit() - they basically are thrown away. Even if you did do

coefficients = polyfit(climb, calories, 2);

you still need to compute the fitted values, like

numFitPoints = 1000; % Enough to make the plot look continuous.
xFit = linspace(min(climb), max(climb), numFitPoints);
yFit = polyval(coefficients, xFit);
hold on;
plot(xFit, yFit, 'r-', 'LineWidth', 2);
grid on;

See attached demo, which produces the plot below.

Best Answer

Related Solutions

MATLAB: Intersection of line and curve from thier points

MATLAB: How to add line of best fit to plot

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