Add trend line to scatter plot with years in the X-axis

I have a scatter plot with Date in the X-axis and length in Y-axis. I have been trying to add a trendline to the plot but I think because of the Date in the X-axis, polyfit or polyval are not working. Is there another way to do it?

scatter(Date, Rift)

c = polyfit(Date Rift, 1)

OR

f=fit(Date, Rift,'poly1')

Answer 1

[Star Strider]

I am not certain what the data are.

Assuming originally a datetime array and a double vector, try something lilke this —

Date = datetime(2004,01,01)+calmonths(0:1:12*16);
Rift = sin(2*pi*(1:numel(Date))/12);

[c,S,mu] = polyfit(datenum(Date), Rift, 1);
trendline = polyval(c,datenum(Date),S,mu);

figure
plot(Date, Rift)
hold on
plot(Date, trendline, '-r')
hold off
grid

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[Anwesha Sharma]

Thank you so much for your reply. This works perfectly.

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

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