Struggling to add the polynomial line

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emily bristow 2020-12-18

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https://ww2.mathworks.cn/matlabcentral/answers/697275-struggling-to-add-the-polynomial-line

评论： emily bristow 2020-12-19

I've managed to use ployfit(X,Y,1) to get the two readings but I'm unsure on how to add the line and caption to the actual plot.

Any help?

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David Goodmanson 2020-12-18

编辑：David Goodmanson 2020-12-18

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Hi emily,

I take it you want to add the fitting straight line to the plot. The output of polyfit is a two-component vector P. Then for an array variable x (which could be the same as X) the fitting line is just y = polyval(P,x). Then you can do, for example

plot(X,Y,x,y)

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采纳的回答

KSSV 2020-12-18

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n = 10 ;

x = 1:n ;

y = rand(size(x)) ;

p = polyfit(x,y,1) ;

yi = polyval(p,x) ;

figure

hold on

plot(x,y,'*r')

plot(x,yi,'b')

legend('Original Points','Fitted Line')

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David Goodmanson 2020-12-18

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Hi emily,

in case you don't want the equation in the title, take a look at the 'text' command.

Also, I have to disagree with KSSV on one detail. I think

plot(x,y,'*r',x,yi,'b')

is a better way to do things, partly because you don't have to use 'hold on'. And if you use 'hold on' and don't use 'hold off' after the plot commands, it can lead to problems later.

emily bristow 2020-12-19