How does one display the fit line in this plot in this situation?

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alpedhuez
alpedhuez 2021-8-20
评论： alpedhuez 2021-8-21
I have a timetable T with
T.date T.vistors T.sales
----------------------------------------
I draw a plot
yyaxis left
plot(T.date, T.visitors)
hold on
yyaxis right
plot(T.date, T.sales)
Now I want to add a regression line of T.sales = a + b*T.visitors on this plot.
I looked at https://www.mathworks.com/matlabcentral/answers/64754-how-can-i-include-an-equation-in-a-scatter-plot-with-linear-regression-line
But this situation seems to be more complex. How to proceed?

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采纳的回答

Sulaymon Eshkabilov
Ran in:
T = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/717514/test.csv');
Warning: The DATETIME data was created using format 'MM/dd/uuuu' but also matched 'dd/MM/uuuu'.
To avoid ambiguity, supply a datetime format using SETVAROPTS, e.g.
opts = setvaropts(opts,varname,'InputFormat','MM/dd/uuuu');
fit_model = polyfit(T.Visitor, T.Sales,1);
TSales_Fit = polyval(fit_model,T.Visitor);
yyaxis left
plot(T.Date, T.Visitor, 'ro', 'markerfacecolor', 'c', 'markersize', 13)
hold on
yyaxis right
plot(T.Date, T.Sales, 'bs', 'markerfacecolor', 'y', 'markersize', 9)
hold on
plot(0:numel(TSales_Fit)-1,TSales_Fit, 'k-', 'linewidth', 2)
legend('Date vs. Visitors', 'Date vs. Sales', 'Fit model: Visitors vs. Sales', 'location', 'northwest')
grid on

更多回答（1 个）

Sulaymon Eshkabilov
You can use these additional steps to get the linear fit model and calculate its values, and then plot them.
fit_model = polyfit(T.visitors,T.sales,1);
TSales_Fit = polyval(fit_model,T.visitors);
yyaxis left
plot(T.date, T.visitors)
hold on
yyaxis right
plot(T.date, T.sales)
hold on
plot(T.visitors, TSales_Fit)
Note that your set x -axis is T.date and what you are trying to plot on top of that is T.visitors (x-axis) vs. Tsales_Fit (y-axis). There is a mismatch. Thus, it is more appropriate to compute fit model: DD=datenum(T.date); TSales_Fit = a + b*(DD-DD(1)+1); and plot the followings:
DD=datenum(T.date);
DD = DD-DD(1)+1;
fit_model = polyfit(DD,T.sales,1);
TSales_Fit = polyval(fit_model,DD);
yyaxis left
plot(T.date, T.visitors)
hold on
yyaxis right
plot(T.date, T.sales)
hold on
plot(T.date, TSales_Fit)
legend('Date vs. Visitors', 'Date vs. Sales', 'Fit model: Date vs. Sales', 'location', 'best')
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Image Analyst
Image Analyst 2021-8-20
编辑：Image Analyst 2021-8-20
Please attach your table T in a .mat file with the paper clip icon if you need any more help. Otherwise we're just guessing.

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