Inserting a linear fit equation and R sq value for a scatter plot

Question

Amardeep Singh 2018-6-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/408003-inserting-a-linear-fit-equation-and-r-sq-value-for-a-scatter-plot

评论： Aries Dwi Siswanto 2021-8-23

I know it is very basic question. I was able to do a linear curve fit for 6 different curves but I am trying to insert the equation and R sq value in the graph, any help would be appreciated.

if true
  % code
x1=[43.4  30.4  37.6  42.2  60.2  37.8  48  54  67.4  47.6  56  66.5];
y1=[6.38  4.37  4.92  4.31  6.65  5.06  6.06  6.67  8.83  6.29  7.08  7.27];
figure
%%Fit: 'NF'.
[x2, y2] = prepareCurveData( x1, y1 );
ft = fittype( 'poly1' );% Set up fittype and options.
[fitresult, gof] = fit( x2, y2, ft, 'Normalize', 'on' );% Fit model to data.
hold on
h1=scatter (x1,y1,'filled','r');
hold on
h2 = plot( fitresult,'r' );% Plot fit with data.
end

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Answer 1

jonas 2018-6-29

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https://ww2.mathworks.cn/matlabcentral/answers/408003-inserting-a-linear-fit-equation-and-r-sq-value-for-a-scatter-plot#answer_326813

编辑：jonas 2018-6-29

在 MATLAB Online 中打开

The R^2 goodness of fit is stored in gof.rsquare. This is one way to display it in the plot together with the equation:

str=['R^2 =',num2str(gof.rsquare),newline,...
'y = ',num2str(fitresult.p1),'x+',num2str(fitresult.p2)]
annotation('textbox',[.15 .9 0 0],'string',str,'FitBoxToText','on')

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Amardeep Singh 2018-7-4

在 MATLAB Online 中打开

I am sorry to say, but both didn't worked out. :( No luck, I tried to modify the code and it just represent R^2 but no value, here is the code.

if true
  % code
if true
% code
x1=[43.4  30.4  37.6  42.2  60.2  37.8  48  54  67.4  47.6  56  66.5];
y1=[6.38  4.37  4.92  4.31  6.65  5.06  6.06  6.67  8.83  6.29  7.08  7.27];
figure
%%Fit: 'NF'.
[x2, y2] = prepareCurveData( x1, y1 );
ft = fittype( 'poly1' );% Set up fittype and options.
[fitresult, gof] = fit( x2, y2, ft, 'Normalize', 'on' );% Fit model to data.
hold on
h1=scatter (x1,y1,'filled','r');
hold on
h2 = plot( fitresult,'r' );% Plot fit with data.
formatspec = 'R^2=','gof.rsquare'
str= sprintf(formatspec,(gof.rsquare))
annotation('textbox',[.15 .9 0 0],'string',str,'FitBoxToText','on')
end
Same Error
Error in Untitled (line 14)
str=['R^2 =',num2str(gof.rsquare),char(10),...
end

but what I want to do is to use this option in the given below code, I've been trying to find solution but all in vain, I will be really thankful for you any advice on this.

ORIGINAL CODE

if true
  % code
%%Fill the Markers
% Create a scatter plot and fill in the markers. |scatter| fills each marker 
% using the color of the marker edge
% Copyright 2015 The MathWorks, Inc.
x1=[43.4  30.4  37.6  42.2  60.2  37.8  48  54  67.4  47.6  56  66.5];
y1=[6.38  4.37  4.92  4.31  6.65  5.06  6.06  6.67  8.83  6.29  7.08  7.27];
x2=[51.6  51.6  50.1  57.4  63  59.4  54.8  64.7  73.5  63.2  65.9  77.6];
y2=[7.22  6.19  5.1  6.02  7.84  8.11  7.43  7.92  9.33  8.91  8.21  8.16];
x3=[58.1  51.5  60.1  60  68.5  62.7  66.5  72.6  74.3  66  69.7  78.3];
y3=[7.27  5.68  7.74  5.94  8.57  8.36  8.44  7.89  9.71  9.28  9.33  8.07];
x4=[54.4  51.9  56.6  63.6  67  55.9  64.4  76.2  72.1  63.7  69.1  79.3];
y4=[6.76  5.95  6.23  5.63  8.21  7.75  8.23  7.16  9.45  8.72  9.3  7.57];
figure
%%scatter plot
%scatter (x1,y1,'filled');
%hold on
%scatter (x2,y2,'filled');
%hold on
%scatter (x3,y3,'filled');
%hold on
%scatter (x4,y4,'filled');
%hold on
%%Fit: 'NF'.
[x5, y5] = prepareCurveData( x1, y1 );
ft = fittype( 'poly1' );% Set up fittype and options.
[fitresult, gof] = fit( x5, y5, ft, 'Normalize', 'on' );% Fit model to data.
hold on
h1=scatter (x1,y1,'filled','r');
hold on
h2 = plot( fitresult,'r' );% Plot fit with data.
hold on
%%Fit: 'SFI'.
[x6, y6] = prepareCurveData( x2, y2 );
ft = fittype( 'poly1' );% Set up fittype and options.
[fitresult, gof] = fit( x6, y6, ft, 'Normalize', 'on' );% Fit model to data.
hold on
h3=scatter (x2,y2,'filled','b');
hold on
h4 = plot( fitresult,'b' );% Plot fit with data.
hold on
%%Fit: 'SFII'.
[x7, y7] = prepareCurveData( x3, y3 );
ft = fittype( 'poly1' );% Set up fittype and options.
[fitresult, gof] = fit( x7, y7, ft, 'Normalize', 'on' );% Fit model to data.
hold on
h5=scatter (x3,y3,'filled','m');
hold on
h6 = plot( fitresult,'m' );% Plot fit with data.
hold on
%%Fit: 'SC-M'.
[x8, y8] = prepareCurveData( x4, y4 );
ft = fittype( 'poly1' );% Set up fittype and options.
[fitresult, gof] = fit( x8, y8, ft, 'Normalize', 'on' );% Fit model to data.
hold on
h7=scatter (x4,y4,'filled','k');
hold on
h8 = plot( fitresult,'k' );% Plot fit with data.
hold on
axis ([25 85 4 11]);
legend ([h1 h3 h5 h7],{'NF','SFI','SFII','SC-M'}, 'location','NW','orientation','horizontal')
xlabel('Compressive Strength (MPa)') % x-axis label
ylabel('Flexural Strength (MPa)') % y-axis label
grid on 
grid minor
end

Amardeep Singh 2018-7-5

Thanks for the help with little modification I was able to do everything, thanks. and my graph look like a happy puppy now.

Aries Dwi Siswanto 2021-8-23

Hi Amardeep Singh,

I'm wondering how to arrange the position of the legend:

red circle NF: y =0.87309x + 8.0233 R2=0.8127

etc.

I'm foolowing your code above, but I could not get the graph as your mentioned above.

Could you please help me?

Thank you very much

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Inserting a linear fit equation and R sq value for a scatter plot

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