how to fit linear trend in time series
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devendra
am 26 Apr. 2014
Kommentiert: Star Strider
am 21 Apr. 2017
i have this time series liner fitted figure but i plotted this figure with the help of matlab tool box((basic fitting)(liner fit)) but i want to do same thing from matlab code.thank you in advance.
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Star Strider
am 26 Apr. 2014
Bearbeitet: Star Strider
am 27 Apr. 2014
See if this does what you want:
% Create Data
yrs = linspace(1,100,100);
rainfall = 0.3*yrs + 350*rand(1,100);
% Fit Data
b = polyfit(yrs,rainfall, 1);
fr = polyval(b, yrs);
% Plot Data & Fit
figure(1)
plot(yrs, rainfall, '-b')
hold on
plot(yrs, fr, '-r')
hold off
h1 = legend('Data', 'Linear', 'Location','NE')
set(h1, 'FontSize',8)
[xlim ylim]
textposx = diff(xlim)*0.50+min(xlim);
textposy = diff(ylim)*0.95+min(ylim);
text(textposx,textposy, sprintf('y = %.2f*x %c %0.2f', b(1), char(45-(sign(b(1))+1)), abs(b(2))), 'FontSize',8)
xlabel('Years')
ylabel('Rainfall (mm)')
EDIT — Added textposx and textposy.
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Muhammad Usman Saleem
am 21 Apr. 2017
@Star Strider I have plot my timeseries plot through this method
myfile=load('time.txt');
xx = myfile(:,2);
dataa=myfile(:,1);
x=xx.';
ts1 = timeseries(x,1:length(x));
ts1.Name = 'Daily Count';
ts1.TimeInfo.Units = 'days';
ts1.TimeInfo.StartDate = '01-Jan-2003'; % Set start date.
ts1.TimeInfo.Format = 'mmm dd, yy'; % Set format for display on x-axis.
ts1.Time = ts1.Time - ts1.Time(1); % Express time relative to the start date.
plot(ts1)
How can i use ploy fit against the time and ts1.Data? My data is a vector but date is in date format. Can you tell me how?
Star Strider
am 21 Apr. 2017
You need to convert the dates and times to date numbers using the datenum function. Use polyfit with 3 outputs so that it will do centring and scaling. Be sure to include all the outputs in your polyval call as well. Use the datetick function to plot the x-axis as the dates and times you want.
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dpb
am 26 Apr. 2014
p=polyfit(y,x);
doc polyfit % for more details
doc polyval % to evaluate
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