How to add line of best fit to plot?

I want to add a line of best fit to my plot using the polyfit function. However, the graph turns blank when I integrate polyfit in my code. How can I change it to make polyfit work?

% original graph without line of best fit
rideData; % file that contains arrays of data/numbers for climb and calories

figure(1);
plot(climb, calories, "o");
xlabel('climb');
ylabel('calories');

% new graph with polyfit. it turns blank
rideData; % file that contains arrays of data/numbers for climb and calories

figure(1);
polyfit(climb, calories, "o");
xlabel('climb');
ylabel('calories');

Answer 1

[Image Analyst]

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.

[Noushin Quazi]

i believe the reference to polyfit in the second code blurb is meant to be polyval

[Image Analyst]

Sorry - you are correct. I'll correct it. Thanks for catching that.