How can I plot two datasets together if they have different x axis values?

I want to plot flux data versus time. I have a dataset of flux values where the x-axis is timestamps (not chronological because I forced the dates to be the same so that my 17-day data shows up as one composite day). I have another vector of hourly mean flux values. I want to plot these as a line over the flux data but the x axis data is not the same as the x coordinates for the individual flux values. I don't know how to tell Matlab to plot both together. I think I need to convert the x coordinates for one dataset into the format of the other but I'm not sure how to do that.

This is what the data looks like

Data 1: x = MX1day (4888x1 double), y = cutflux (4888x1 double)

Data 2: x = 1:24, y = mfbin (24x1 double)

I have attached data.mat which includes MX1day, cutflux, and mfbin

I plotted the data in two separate subplots (see attached). Hopefully this makes it easier to see my problem. The hour numbers from the lower plot should be the same as the hourly ticks about but I'm not sure how to tell it to plot that way on the same axes.

This is how I am plotting the attached figure

figure

subplot(2,1,1)

hold on; box on;

for i= 1:length(days)

plot(MX1day(days{i}),cutflux(days{i}),'.','color',colors(i,:),'markersize',10)

end

legend('July 23','July 24','July 25','July 26','July 27','July 28','July 29','July 30','July 31',...

'Aug 1','Aug 2','Aug 3','Aug 4','Aug 5','Aug 6','Aug 7','Aug 8','Aug 9')

set(gca,'fontsize',20)

ylabel('O_2 Flux (mmol/m^2/hr)')

datetickzoom

subplot(2,1,2)

hold on; box on;

plot(1:24,mfbin,'k','linewidth',3)

xlim([0 24])

ylim([-150 150])

set(gca,'fontsize',20)

ylabel('O_2 Flux (mmol/m^2/hr)')

Answer 1

[Star Strider]

The ‘data.mat’ file contains data for only one day as datenum values, that apparently are all for 01-Jan-2020.

One approach:

D = load('data.mat');
MX1day = D.MX1day;
cutflux = D.cutflux;
mfbin = D.mfbin;

DT = datetime(MX1day,'ConvertFrom','datenum');
hrs = min(DT)+hours(1:24);

figure
plot(DT, cutflux, '.')
hold on
plot(hrs, mfbin, '-k', 'LineWidth',3)
hold off
xtickformat = 'HH';

producing:

I have no idea if this will work for all your days, since I don’t have them to experiment with. It works here.

[Heidi Hirsh]

Thank you! This is exactly what I want! Those are actually all my days. I changed the date value for every timestamp to the same day so that the hours for each day of my deployment would plot on a single composite day :)

I have one follow-up question. I am trying to shade night-time. I managed to shade from 1:00 to 7:00 and 19:00 to 24:00 but I cannot figure out how to shade before 1am for the first hour. Do you know how I can do this?

I am using the fill function like this:

h=fill([hrs(1) hrs(1) hrs(7) hrs(7)],[y -y -y y],[.6 .6 .8])

set(h,'EdgeColor','none')

set(h,'facealpha',0.2)

h=fill([hrs(19) hrs(19) hrs(24) hrs(24)],[y -y -y y],[.6 .6 .8])

set(h,'EdgeColor','none')

set(h,'facealpha',0.2)

[Heidi Hirsh]

And can I make it not add the 'Jan 01, 2020' label on the x axis?

[Star Strider]

Try this:

figure
plot(DT, cutflux, '.')
hold on
plot(hrs, mfbin, '-k', 'LineWidth',3)
fill([hrs(1:7), fliplr(hrs(1:7))], [ones(1,7)*min(ylim) ones(1,7)*max(ylim)], 'b', 'FaceAlpha',0.2)
fill([hrs(19:24), fliplr(hrs(19:24))], [ones(1,6)*min(ylim) ones(1,6)*max(ylim)], 'b', 'FaceAlpha',0.2)
hold off
xtickformat = 'HH';

I cannot find out where the 'Jan 01, 2020' label is, so I cannot turn it off or delete it. I will keep looking, however it may not be possible to do that.

[Heidi Hirsh]

Thank you! Unfortunately that shading looks like it still starts at 01:00 instead of midnight. I'm not sure how to start earlier since hrs(0) isn't a thing.

And no worries about the label. I can always cut it out of the final figure using a different program.

[Heidi Hirsh]

I fixed it! I made a new vector for the x values (based on your previous help):

hrs2 = min(DT)+hours(0:24)

and then I was able to start the shading at hrs2(1) which is now 00:00.

I really appreciate your help!

[Star Strider]

My pleasure!

This gets the shading correct, considering the limitations of your data, however the rest may not be possible:

DT = datetime(MX1day,'ConvertFrom','datenum');
hrs = min(DT):hours(1):max(DT);

figure
plot(DT, cutflux, '.')
hold on
plot(hrs, mfbin, '-k', 'LineWidth',3)
fill([hrs(1:8), fliplr(hrs(1:8))], [ones(1,8)*min(ylim) ones(1,8)*max(ylim)], 'b', 'FaceAlpha',0.2)
fill([hrs(19:24), fliplr(hrs(19:24))], [ones(1,6)*min(ylim) ones(1,6)*max(ylim)], 'b', 'FaceAlpha',0.2)
hold off

.

[Heidi Hirsh]

Thank you!

I like how you redefined hrs. Oddly it looks like the second interval now shades 18:00 to 23:00 instead of 19:00 to 24:00

[Star Strider]

As always, my pleasure!

I needed to take a break.

This gets closer:

DT = datetime(MX1day,'ConvertFrom','datenum');
hrs = min(DT):minutes(1):max(DT);

figure
plot(DT, cutflux, '.')
hold on
plot(hrs(1:60:end), mfbin, '-k', 'LineWidth',3)
fill([hrs(1:420), fliplr(hrs(1:420))], [ones(1,420)*min(ylim) ones(1,420)*max(ylim)], 'b', 'FaceAlpha',0.2)
fill([hrs(end-299:end), fliplr(hrs(end-299:end))], [ones(1,300)*min(ylim) ones(1,300)*max(ylim)], 'b', 'FaceAlpha',0.2)
hold off

The rest of the code is unchanged.