How to add error bars to a timeseries plot using datetime values
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Hi all,
Please can someone help me figure out how to add error bars to my timeseries! I am gaving a problem figuring out what the x axis values should be. Would be much appreciated. (I'm new to Matlab!)
Context
I have a timeseries plot that runs Dec 17th - May 30th (alternate days). This is the code for my timeseries plot:
ts1 = timeseries(SSS_SGeast_anom_av_series, 1:2:166);
ts1.Name = ('Average salinity anomaly (psu)');
ts1.TimeInfo.Units = 'days';
ts1.TimeInfo.StartDate = '17-Dec-2020'; % Set start date.
ts1.TimeInfo.Format = 'dd mmm yy'; % Set format for display on x-axis.
ts.TimeInfo.Increment = '2';
ts1.Time = ts1.Time - ts1.Time(1); % Express time relative to the start date.
plot(ts1, '- k .', 'MarkerSize', 10, 'Linewidth', 2);
hold on
My standard deviation vector is a double numeric vector, size 83 x 1. I want to add this data as error bars on to my timeseries plot, using the command:
I have set y to by the timeseries y values (SSS_SGeast_anom_av_series), and err to be the standard deviation vector mentioned above.
Problem
I can't figure out what x values I need to suit the errorbar command above?
I think I need to somehow extract the datetime values from my original timeseries and then use these, but I can't figure out how to get those values.
Either that or make a new vector of the date values, and convert this to datetime. I'm not sure.
Please help if you can! Or let me know if I've been unclear.
采纳的回答
I have formatted errorbar to not draw a line connecting the data points. Technically, the marker isn't necessary either, but I wanted to keep this example simple.
% Create a data set
y = randn(83,10);
SSS_SGeast_anom_av_series = mean(y,2);
ts1 = timeseries(SSS_SGeast_anom_av_series, 1:2:166);
ts1.Name = ('Average salinity anomaly (psu)');
ts1.TimeInfo.Units = 'days';
ts1.TimeInfo.StartDate = '17-Dec-2020'; % Set start date.
ts1.TimeInfo.Format = 'dd mmm yy'; % Set format for display on x-axis.
ts.TimeInfo.Increment = '2';
ts1.Time = ts1.Time - ts1.Time(1); % Express time relative to the start date.
plot(ts1, '- k .', 'MarkerSize', 10, 'Linewidth', 2);
hold on
errorbar(ts1.Time,ts1.Data,std(y,[],2),'k.')
hold off
7 个评论
Mairead Smith
2021-7-14
Cris LaPierre
2021-7-14
My use of std was just a way for me to create errorbars here since I had to create my own data. You should replace anything I created to get this example to work with your actual data.
Mairead Smith
2021-7-14
There are a couple issues to point out. First, ts.TimeInfo.StartDate must be one of the accepted character vector formats. Click here for a list of valid character vector formats.
While there, I also noticed that timeseries objects do not officially support 'months' as a unit. The code does appear to work with it set to months, but that's something to be aware of. Your Time values may not be what you expect.
Time Data:1
'01-Dec-2020 00:00:00' -0.123895243023677
'31-Dec-2020 10:30:00' 0.0516582570769676
'30-Jan-2021 21:00:00' 0.443403815055329
'02-Mar-2021 07:30:00' 1.84363664335436
'01-Apr-2021 18:00:00' 0.514591415320431
I also appear to have mispoken about extracting time. ts.Time returns the values that were entered for the timevals input (here that is 1:5). That works when your unit was days, but not when it is months. Use getabstime and datetime to extract time as formatted in the timeseries object.
Finally, errorbar appears to only like column vectors. Transpose your data and it should work.
Pos_anom_series = [-0.123895243023677, 0.0516582570769676, 0.443403815055329, 1.84363664335436, 0.514591415320431]';
Pos_anom_std_dev = [0.866800000000000, 0.564300000000000, 0.749800000000000, 1.58430000000000, 0.921700000000000]';
ts = timeseries(Pos_anom_series, 1:5);
ts.Name = 'Average chlorophyll anomaly';
ts.TimeInfo.Units = 'months';
ts.TimeInfo.StartDate = '01-Dec-2020'; % Set start date.
ts.TimeInfo.Format = 'mmm yy'; % Set format for display on x-axis.
ts.Time = ts.Time - ts.Time(1); % Express time relative to the start date.
plot(ts, '--ro')
grid on
hold on
e = errorbar(datetime(getabstime(ts)), ts.Data, Pos_anom_std_dev);
e.LineStyle = 'none';
hold off
Remember your hold on must come before your second plotting command. Also, it is best practice to always have a matching hold off.
Given all the issues mentioned above, I wonder if it wouldn't make more sense to update your code to use a timetable. I'm not sure the reasons you elected to use a timeseries object, but you'll find timetables offer many of the same benefits. The equivalent code could be the following:
Pos_anom_series = [-0.123895243023677, 0.0516582570769676, 0.443403815055329, 1.84363664335436, 0.514591415320431]';
Pos_anom_std_dev = [0.866800000000000, 0.564300000000000, 0.749800000000000, 1.58430000000000, 0.921700000000000]';
% Create data
Time = datetime(2020,12,01) + calmonths(1:5)';
Data = Pos_anom_series;
stdev = Pos_anom_std_dev;
% create timetable
dataTT = timetable(Time,Data,stdev)
% create plot
errorbar(dataTT.Time, dataTT.Data, dataTT.stdev,'--ro')
grid on
title('Average chlorophyll anomaly')
ylabel('Average chlorophyll')
xtickformat('MMM yy')
Mairead Smith
2021-7-14
Cris LaPierre
2021-7-14
Possibly, but without knowing what the error message is, I wouldn't want to say. What happens if you copy and paste the code I've shared? Does that run without error?
Consider saving your variables to a mat file and attaching it to your post using the paperclip icon. Also copy/paste the code you are running (all the code needed to reproduce the error), as well as the full error message (all the red text).
更多回答（1 个）
Sulaymon Eshkabilov
2021-7-14
Maybe you should try to employ datenum(), e.g.:
x= datenum(ts1); % See help doc how to get datenum()
errorbar(x,y,ERR);
How to use datenum(): https://www.mathworks.com/help/matlab/ref/datenum.html#d123e278633
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