Add 2 trendlines to scatter plot

Hi, I want to make a scatter plot and then add a liner fit line as well as a exponential fit line to the scatter plot and display the equations on on the plot.

I know how to plot the exponential fit line using:

x = SZA15(:,9);
y = SZA15(:,5);  
f = fit(x,y,'exp1')
  plot(f,x,y)

but I am not sure how to do the linear fit line.

[dpb]

Not sure if you got this far where the problem is...

f2 = fit(x,y,'poly1');
hold all
plot(f2,x,y)

should do it, doesn't it?

Answer 1

[Mishaal Aleem]

Similar to how you use the fit command to find the exponential fit, you can use it to find the linear fit by using 'poly1' as the fitType argument. Please see the fitType section of the fit documentation for information.

To display the equations on on the plot, you can implement this workaround from a similar MATLAB Answers question.

Assuming you would like to display the equation in the plots legend, please try the below code:

x = SZA15(:,9);
y = SZA15(:,5);  

fits{1} = fit(x,y,'exp1'); %Exponential Fit Model
fits{2} = fit(x,y,'poly1'); %Linear Fit Model
hold on
plot(x,y,'o'); %Plot raw data as circles
plot(fits{1},'r');
plot(fits{2},'b');

str = {'Data'};
%Extact the equations
for i = 1:numel(fits)
    % Generate the equation for each fit
    eq = formula(fits{i}); %Formula of fitted equation
    parameters = coeffnames(fits{i}); %All the parameter names
    values = coeffvalues(fits{i}); %All the parameter values
        for idx = 1:numel(parameters)
              param = parameters{idx};
              l = length(param);
              loc = regexp(eq, param); %Location of the parameter within the string
              while ~isempty(loc)   
                  %Substitute parameter value
                  eq = [eq(1:loc-1) num2str(values(idx)) eq(loc+l:end)];
                  loc = regexp(eq, param);
              end
        end
        str{i+1} = eq; %append fit equation
end
legend(str); %display equations in legend