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How can I add a a best fit line, a scatter plot data? having trouble

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juan Ortiz
juan Ortiz 2019-4-6
回答： Saeed Bello 2021-8-29
% using the excel data
[FileName, PathName] = uigetfile('*.xlsx','Select Excel files to analyze:','MultiSelect','off');
[status, sheets] = xlsfinfo([PathName, FileName]);
data_summary = xlsread([PathName, FileName],sheets{1});
% using struct to structure the data
data = struct('Heights',[],'Qs',[]);
data.heights=(data_summary(1:5,1));
data.flowrates=(data_summary(1:5,2:11));
figure (1)
for i=1:5
subplot(2,3,i)
histogram(data.flowrates(i,1:10),10)
xlabel('Volumetric flow rates [mL/s]','FontSize',10,'FontWeight','bold');
ylabel('Number of occurances','FontSize',10,'FontWeight','bold');
legend(['water exit height=' num2str(data.heights(i))]);
end
% Adding the average flow rate histogram
Qavg=mean(data.flowrates,2);
Qstd=std(data.flowrates,0,2);
errQ=Qstd./2;
subplot(2,3,6)
% fit=polyfit(data.flowrates,1);
% plot(polyval(fit,data.heights))
errorbar(data.heights,Qavg,errQ,'ro')
xlabel('Water exit height [cm]','FontSize',10,'FontWeight','bold');
ylabel('Flow rate [ml/s]','FontSize',10,'FontWeight','bold');
**
% I keep getting an error with what I have so far

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回答（2 个）

Cris LaPierre
Cris LaPierre 2019-4-6
I'd use polyfit.
This example shows you to do a simple linear regression.
x = 1:50;
y = -0.3*x + 2*randn(1,50);
p = polyfit(x,y,1);
f = polyval(p,x);
plot(x,y,'o',x,f,'-')
legend('data','linear fit')
Saeed Bello
Saeed Bello 2021-8-29

Just add lsline after your scatter plot expression. For example

scatter(x,y)
lsline

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