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use the result of the fit function as a legend in a plot

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ignacio bobadilla tapia
ignacio bobadilla tapia on 29 Jul 2021
Commented: KSSV on 29 Jul 2021
Hello everyone, I wanted to ask how I can make the legend of the graph be the result of the linear regression that is done with the command 'fit', and that polynomial represent it in the legend, for example y = ax + b, there will be some way to do it automatically or is it done manually?. Thanks.
reg=load('regression.txt')
ft=fit(reg(:,1),reg(:,2),'poly1')
plot(ft,'-r',reg(:,1),reg(:,2),'ob')

Answers (1)

KSSV
KSSV on 29 Jul 2021
Edited: KSSV on 29 Jul 2021
load census;
f=fit(cdate,pop,'poly2') ;
h = plot(f,cdate,pop) ;
legendinfo = legend(h) ;
f
f =
Linear model Poly2: f(x) = p1*x^2 + p2*x + p3 Coefficients (with 95% confidence bounds): p1 = 0.006541 (0.006124, 0.006958) p2 = -23.51 (-25.09, -21.93) p3 = 2.113e+04 (1.964e+04, 2.262e+04)
legendinfo.String{2} = formula(f) ;
  2 Comments
KSSV
KSSV on 29 Jul 2021
load census;
f=fit(cdate,pop,'poly2') ;
eq = formula(f); %Formula of fitted equation
parameters = coeffnames(f); %All the parameter names
values = coeffvalues(f); %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
h = plot(f,cdate,pop) ;
legendinfo = legend(h) ;
legendinfo.String{2} = eq;

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