How can I plot two different datetime vectors in the same graph?

Hi All,

I have two datetime vectors (time1 and time2) with different sample period and different lengths.

Each of these vectors corresponds to different variable. For example - the first vector (time1) corresponds to to water velocity (V) in a river, and the second (time2) to rain intensity (R).

Since they cover the same time range (April to November, 2018) I would like to plot them on the same graph. However, I don't seem to manage doing so, probably because they differ in length and sample frequency.

Could anyone share any solution to that?

Thanks, Ron

[Caglar]

Hello, did you try plot(...); hold on; plot(...)?

[Walter Roberson]

Or

plot(time1, V, time2, R)

[Ron Nativ]

This doesn't seem to work. See the attached graph. Also notice the X axis which is not in a datetime format (although the vectors are!)

[madhan ravi]

plotyy?

[Caglar]

@Ron Nativ It seems to me that problem is about something else. Can you post more of your code, or better, a minimum working example.

[Walter Roberson]

Which MATLAB version are you using?

[Ron Nativ]

Thank you all for answering, Caglar, you are right, the problem was not related to the specific graphic coding, but to my data handling. Sorry for that and thanks again!

Answer 1

[Caglar]

Comment if any part is not clear.

first_date_array=datetime('today'):days(1):datetime('today')+days(10); %array for 10 days
first_data=1:1:11;
second_date_array=datetime('today'):days(2):datetime('today')+days(15); %array for 15 days and it has data for each 2nd day only
second_data=8:-1:1;
figure(1); %method 1: plot them together
plot(first_date_array,first_data,'o',second_date_array,second_data,'o'); %x,y,markershape,x,y,markershape
xlabel('Datetime'); ylabel('Data')
legend('First','Second')
figure(2); %method 2: add new plots using hold on
plot(first_date_array,first_data,'o');
hold on
plot(second_date_array,second_data,'o');
xlabel('Datetime'); ylabel('Data')
legend('First','Second')

Answer 2

[madhan ravi]

Or try

yyaxis right 
plot(time1, V)

yyaxis left
plot(time2, R)

See https://www.mathworks.com/matlabcentral/answers/5456-get-plotyy-second-axis-handle#answer_7638 for grabbing handles of each axis

Also notice the X axis which is not in a datetime format (although the vectors are!)

xtickformat('dd-MMM-yyyy')

An example:

t = datetime(2014,6,28) + calweeks(0:9);
y = rand(1,10);
yyaxis left
plot(t,y);
y = 1:10;
yyaxis right
plot(t,y(1:numel(t)));
AX=findall(0,'type','axes');
AX(2)                          %grabs second axis handle experiment and see by scrolling the graph
xtickformat(AX,'dd-MMM-yyyy')