MATLAB: Plotting time/date on surf or mesh plot

date time surfaceplot

I'm trying to plot time&date on a surface but can't get it to look right. It's a time period between 1920-2019 where measurements are scattered in between those years, som years more measurements than other years. Dates where in Julian days to start with and have been converted to datetime. Which I have tried to plot it in, but couldnt get to work.

After that, I tried with just years. This looked fine on the labels, but with all the data from that year in spot didnt look very representative. I also tried converting YYMMDD format and it didn't look very good either.

Any advice on how i could do this? It would be greatly appreciated.

Best Answer

surf can handle datetime and duration data. Let's create some sample datetime data and use that to compute a duration.

[d1, d2] = meshgrid(datetime('now')+days(0:10));
z = d1-d2;

Plot it as a surface.

h = surf(d1, d2, z);

I would prefer the Z axis labels to be in units of days rather than hours, minutes, and seconds. Let's change the format on those labels. First we need to get the axes that contains the surface plot.

ax = ancestor(h, 'axes');

Now set the format of the Z axis labels to 'd' to show them in units of days.

Technically I didn't need to get the axes handle ax, but this ensures that if there are multiple axes open (potentially in multiple figures) I'm changing the format for the correct axes.

ztickformat(ax, 'd')

Related Solutions

MATLAB: Put the name in the “x axis” of the graph bar every five days or seven days

Don't put the ticks every day; that's the cause for there being that many--you did it to yourself! :)

The bar() command will put ticks at convenient places automagically, if you don't like those you can then put them where want.

Use xticklabel to write something besides the tick value.

If you would convert to use datetime, you could get the day string for free...

ADDENDUM:

Sorry, got sidetracked and didn't get back when thought would/could...

It's relatively simple to use dates for the x axis and then the datetime ruler object gives you a lot of flexibility for dates --I'll also demonstrate the new(ish) MATLAB table object in lieu of the old xlsread route...

tEnersol=readtable('enerosolar.xlsx','Sheet','EneDic');  % read into a table object
tEnersol.Properties.VariableNames={'Rad','Dia'};         % assign variable names
yr=2014;                                                 % need the proper year 
tEnersol.Date=datetime(yr,1,tEnersol.Dia);               % and create a date column
hB=bar(tEnersol.Date,tEnersol.Rad);                      % bar plot against actual date
hAx=gca;                                                 % get axes handle...
xlim([datetime(2014,1,1) datetime(2015,1,1)])            % set limit to cover the full year
hAx.XAxis.TickLabelFormat='eee';                         % show day of week

produced

which you'll note doesn't have the same shape as yours as it is plotted using the actual date in the data file on the x axis, not against ordinal position in the file (which is not ordered by date). This will show up if change the time format on the x-axis to 'MMM'

which illustrates the data must be from somewhere in the northern hemisphere.

MATLAB: Function that transforms years into days

Like this?

function numDay = year2days(year)
  numDay = days(datetime(year,12,31)-datetime(year,1,1))+1;
end

The following is one example:

>> year2days(2000)
ans =
 366

Best Answer

Related Solutions

MATLAB: Put the name in the “x axis” of the graph bar every five days or seven days

MATLAB: Function that transforms years into days

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