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Time Series in MATLAB

How to plot date and time in MATLAB. An example of a time-series plot.

Converting time series plots from MATLAB to plotly requires a few extra steps. Since MATLAB is extremely flexible with how the dates can be formatted within the X and Y tick labels, automatically parsing the various permutations of the date labels is nearly impossible. Here are two options for plotting time series in MATLAB with Plotly.

Converting to a Standard Date Format

The first way to convert MATLAB time series plots is to convert the dates to unix time with the convertDate function included in Plotly MATLAB toolbox.
  1. Convert your MATLAB time values to the "milliseconds from 1969" time format with convertDate below.
  2. Run >> plotlyfig = fig2plotly(gcf) to parse your figure.
  3. Modify the converted figure's date axes: plotlyfig.layout.xaxis1.type = 'date';
    Note: the xaxis1 might be xaxisN—> depending on the number of axes you have, where N is the id of the axis you wish to modify.
  4. Change the file option to overwrite your newly created plot:
    >> plotlyfig.PlotOptions.FileOpt = 'overwrite';
  5. Send your figure back to Plotly:
    >> plotly(plotlyfig);
Example
x = linspace(datenum(2009,01,01),datenum(2010,01,01),12);
y = rand(1,12);
plotlydate = convertDate(x);
plot(plotlydate,y);
plotlyfig = fig2plotly(gcf,'filename','myfig');
plotlyfig.layout.xaxis1.type = 'date';
plotlyfig.PlotOptions.FileOpt = 'overwrite';
plotly(plotlyfig);

Explicitly Setting the Date Format

A second way to convert MATLAB time series plots to Plotly is by explicitly setting the date-time format.
  1. set the date-string format, for example: userdata.plotly.xdateformat = ‘yyyy:mm:hh’;
  2. set(your_axis_handle, ‘UserData’, userdata)
  3. Send your figure to plotly: plotlyfig = fig2plotly(gcf);
Example
startDate = datenum('01-01-2009');
endDate = datenum('12-31-2009');
xData = linspace(startDate,endDate,12);
plot(xData,rand(1,12))
set(gca,'XTick',xData)
dateformat = 'yy:mmm';
datetick('x',dateformat,'keepticks')
userdata.plotly.xdateformat = dateformat;
set(gca,'UserData',userdata)
p = fig2plotly(gcf);
% Learn about API authentication here: https://plot.ly/matlab/getting-started
% Find your api_key here: https://plot.ly/settings/api

data = {...
  struct(...
    'x', { {'2013-10-04 22:23:00', '2013-11-04 22:23:00', '2013-12-04 22:23:00'} }, ...
    'y', [1, 3, 6], ...
    'type', 'scatter')...
};
response = plotly(data, struct('filename', 'date-axes', 'fileopt', 'overwrite'));
plot_url = response.url
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