Polyfit: How to use?

Question

Sarah Kirchler 2020-7-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/562844-polyfit-how-to-use

回答： Cris LaPierre 2020-7-10

采纳的回答： Cris LaPierre

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Dear MatLab community!

I'd like to lay a line of best fit in my scatterplot.

I did the following:

figure;scatter(stimsAt10Hz_outdet(:,1),AQS(:,2), 40, [0.2 0.35 1], 'filled')
grid on
xlabel('Magnitude(z)')
ylabel('ASQ-Score')
title('Corr(Contour,ASQ)')
polyfit(stimsAt10Hz_outdet, AQS,1)

But nothing happens.

Do anyone find the error? I am not sure if I used polyfit in the right way..

I would be really thankful to hear something from you.

Thank you in advance!

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Answer 1

Cris LaPierre 2020-7-10

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/562844-polyfit-how-to-use#answer_464048

I recommend using the examples in the documentation to guide you.

Here, you must use the exact same x and y values that you used in your plot command: stimsAt10Hz_outdet(:,1),AQS(:,2). You are passing in more. Polyfit does not know how to handle the extra data.

Polyfit also only returns the coefficients. Use polyval to calculate your fit's y values from a provided x vector. Then use hold on and plot commands to add your fit lines to your figure. See this example.