Use timetable as x axis in heatmap

Question

Amir Hosein Shokouhy 2022-3-10

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https://ww2.mathworks.cn/matlabcentral/answers/1668594-use-timetable-as-x-axis-in-heatmap

回答： Benjamin Kraus 2022-3-12

采纳的回答： Peter Perkins

在 MATLAB Online 中打开

Hello,

I have this time table (t_avg) and I want to use it as the x axis for a heatmap of my load data (load_avg).

I am currently using this code but the x axis is not the correct time:

figure (4)
h=heatmap(load_avg');
XLabels = 1:size(load_avg,1);
CustomXLabels = string(XLabels);
CustomXLabels(mod(XLabels,10) ~= 0) = " ";
h.XDisplayLabels = CustomXLabels;
caxis([0 max(max(load_avg))])
colormap jet
xlabel('Time');
ylabel('Unit');

I tried using this code but it didn't work:

heatmap(t_avg,'XVariable','Time',load_avg');

I'd appreciate it if any one can help.

Thanks,

Amir

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Answer 1

Peter Perkins 2022-3-11

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Amir, according to your screenshots, you do NOT have a timetable. You have a table containg one datetime variable, and a separate double matrix. You need to make a timetable. One possibility might be

tt = timetable(t_avg.Time,load_avg)

another might be

tt = array2table(load_avg,'RowTimes',t_avg.Time)

but I have no idea what you are doing, so I can't really say how to make the timetable.

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Amir Hosein Shokouhy 2022-3-11

Thanks Peter, it's working now. Just one thing, how can I only display the hour and minute and not the second?

Peter Perkins 2022-3-11

help datetime/string

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Answer 2

Benjamin Kraus 2022-3-12

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In this case, you may be better off with something like imagesc or surf instead of heatmap. heatmap is designed for cases in which your x and y dimensions are categorical in nature. In your case, your x-axis is time, which is continuous (even if your data has been discretized). This will let you work with the datetime data more natively, rather than resorting to manually generating your tick labels.

I recommend something like this:

y = 1:size(load_avg,2);
surf(t_avg.Time, y, load_avg');
view(2)
axis tight
caxis([0 max(max(load_avg))])
colorbar
colormap turbo % turbo is more percetually uniform than jet, but otherwise very similar
xlabel('Time');
ylabel('Unit');
xtickformat('hh:mm')