How can I plot dates?

Hello,

How can I plot date in x-axis?

My csv file import dates as: '03/27/2020 19:10:35.537'

My code:

D = data{:,2}; 
d = datenum(D);
date = datetime(d,'Format','dd-MM-yyyy HH:mm:ss.SS','convertFrom','datenum');

As a result, I have my plots good, but only in same data (see Figure).

All my data has the same time, and have the same format 805 x 1 (double). For example, yellow line(good) and blue line (wrong) should be the same on x-axis.

Answer 1

[Cris LaPierre]

I think we need to see your plot command to say for certain what is happening.

My recommendation would be to have your X data be the datetime variable. MATLAB is able to use that as X, and will may the XTickLabels the dates, which are easier to understand.

I would therefore use readtable to load the csv file. That way, I can import the dates directly as datetimes.

[Márcio Gonçalves]

Thanks for answer.

I am already import with readtable. However i have an error with plotting datetimes directly

Error using plot
Invalid data argument.
Error in hygrothermal_cyclesv2 (line 159)
plot(date, T1D,'b--','LineWidth',1);

Please see my code:

data = readtable('test1.csv'); 

D = data{:,2}; % Data
d = datenum(D);
date = datetime(d,'Format','dd-MM-yyyy HH:mm:ss.SS','convertFrom','datenum');

%termopares
T1D = (data{:,3}); % termopar 1D - canal 101
T2D = (data{:,4}); % termopar 2D - canal 102
T3D = (data{:,5}); % termopar 3D - canal 103
T4D = (data{:,6}); % termopar 4D - canal 104
...
%----------------------------------------------------------------------
figure()
set(gcf,'color','w');
set(gca,'fontsize', 18)

plot(date, T1D,'b--','LineWidth',1);
hold on 
plot(date, T2D,'b','LineWidth',1);
hold on 
plot(date, T3D,'g--','LineWidth',1);
hold on 
plot(date, T4D,'g','LineWidth',1);
hold on 
...
plot(inside,'k--','LineWidth',1);
 hold on
plot(outside,'k:','LineWidth',1);
 hold on
datetick('x','HH:MM:SS');
xlabel(('Date'), 'FontSize',18)
ylabel(('Temperature [ºC]'),'FontSize',18);
legend('T1D','T2D', 'T3D', 'T4D','T5D', 'T6D','T7D','T8D','T9D','T10D','inside','outside','Location','eastoutside','FontSize',18);
title('Layer D','FontSize',20);

[Cris LaPierre]

Any chance you can share your file test1.csv? If so, please attach it to your post.

In the meantime, you only need to turn hold on once for an axes. Once you are done plotting to that axes, it's also best practice to then turn it off.

[Cris LaPierre]

In the meantime, I mocked up a simple example using the data format you mentioned. Here is how I might do it. Replace 'Var#' with whatever the variable names are in your table.

data = readtable('test1.csv');
data.Var2.Format = 'dd-MM-yyyy HH:mm:ss.SS';

plot(data.Var2,data.Var3,'b--','LineWidth',1)
hold on
plot(data.Var2,data.Var4,'b--','LineWidth',1)
plot(data.Var2,data.Var5,'g--','LineWidth',1)
plot(data.Var2,data.Var6,'g--','LineWidth',1)

hold off

[Márcio Gonçalves]

I attached my csv file. The time is in colum 2.

thanks

[Cris LaPierre]

The best way to figure out how to read in the data is the Import Tool. It allows you to interactively set the data types, variable names, and visually inspect the results. Once you have it working, you can generate an import script or function for reuse.

Here's a short video that walks you through the steps.

With your data file, I went through and manually created the code to import the data and then format the data. Here's what that ended up looking like.

% Define the import options
opts = detectImportOptions('Marcio_mytest1.csv');
opts.DataLines = [2,inf];
opts.Delimiter = ";";
opts.VariableNames = {'Sweep','Time','Ch101','Ch102','Ch103','Ch104','Ch105',...
    'Ch106','Ch107','Ch108','Ch109','Ch110','Ch111','Ch112','Ch113','Ch114','Ch115',...
    'Ch116','Ch117','Ch118','Ch119','Ch120','Ch201','Ch202','Ch203','Ch204','Ch205',...
    'Ch206','Ch207','Ch208','Ch209','Ch210','Ch211','Ch212','Ch213','Ch214','Ch215',...
    'Ch216','Ch217','Ch218','Ch219','Ch220','Ch301','Ch302','Ch303','Ch304','Ch305',...
    'Ch306','Ch307','Ch308','Ch309','Ch310','Ch311','Ch312','Ch313','Ch314','Ch315',...
    'Ch316','Ch317','Ch318','Ch319','Ch320'};
opts = setvartype(opts,[1,3:62],"double");
opts = setvartype(opts,'Time',"datetime");
opts = setvaropts(opts, 'Time', "InputFormat", "MM/dd/yyyy HH:mm:ss.SSS");

% Read in the data file
data = readtable('test1.csv',opts);

% Set display date format
data.Time.Format = 'dd-MM-yyyy HH:mm:ss.SS';

% Plot
plot(data.Time,data.Ch101,'b--','LineWidth',1)
hold on
plot(data.Time,data.Ch102,'b--','LineWidth',1)
plot(data.Time,data.Ch103,'g--','LineWidth',1)
plot(data.Time,data.Ch104,'g--','LineWidth',1)
hold off

[Cris LaPierre]

If you want to specifically set the display format of the data on the axes, use the datetick function.

EDIT: Don't use datetick. Try xtickformat.

[Peter Perkins]

Don't use the datetick function unless you have a veru old version of MATLAB. Stay away from datenum, datestr, and datetick. In fact, no offense to earlier responders intended, don't do any of that.

In a recent version of MATLAB, here's all you need:

>> tt = readtimetable('test1.csv','RowTimes','Time','PreserveVariableNames',true);
>> head(tt)
ans =
  8×61 timetable
             Time              Sweep #    Chan 101 (C)    Chan 102 (C)    Chan 103 (C)    Chan 104 (C)    Chan 105 (C)    Chan 106 (C)    Chan 107 (C)    Chan 108 (C)    Chan 109 (C)    Chan 110 (C)    Chan 111 (C)    Chan 112 (C)    Chan 113 (C)    Chan 114 (C)    Chan 115 (C)    Chan 116 (C)    Chan 117 (C)    Chan 118 (C)    Chan 119 (C)    Chan 120 (C)    Chan 201 (C)    Chan 202 (C)    Chan 203 (C)    Chan 204 (C)    Chan 205 (C)    Chan 206 (C)    Chan 207 (C)    Chan 208 (C)    Chan 209 (C)    Chan 210 (C)    Chan 211 (C)    Chan 212 (C)    Chan 213 (C)    Chan 214 (C)    Chan 215 (C)    Chan 216 (C)    Chan 217 (C)    Chan 218 (C)    Chan 219 (C)    Chan 220 (C)    Chan 301 (VDC)    Chan 302 (VDC)    Chan 303 (VDC)    Chan 304 (VDC)    Chan 305 (VDC)    Chan 306 (VDC)    Chan 307 (VDC)    Chan 308 (VDC)    Chan 309 (VDC)    Chan 310 (VDC)    Chan 311 (VDC)    Chan 312 (VDC)    Chan 313 (VDC)    Chan 314 (VDC)    Chan 315 (VDC)    Chan 316 (VDC)    Chan 317 (VDC)    Chan 318 (VDC)    Chan 319 (C)    Chan 320 (C)
    _______________________    _______    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ____________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ______________    ____________    ____________
    03/27/2020 19:10:35.537       1           15.4            15.4            15.3            15.2              16            15.5            15.4            15.3            15.3            15.3            20.3            20.8            20.5              21            20.1            20.2            20.2            20.3            19.1              19            18.3            19.3            18.2            19.5            17.8            18.6              23            15.8            15.7            20.5            21.1            20.8            20.4            22.6            20.5            20.5            19.7            21.1            19.6            16.2             20.5              73.1             -24.3              99.6                20              74.9              19.9              82.7                20              81.3              15.9              100             4.34e-05          4.07e-05         -3.79e-05            -4e-05         -3.97e-05         -5.59e-05             18            18.6    
    03/27/2020 19:15:35.536       2           15.4            15.4            15.3            15.2              16            15.5            15.4            15.3            15.4            15.3              21            21.4            21.1            21.8            20.8            20.9            20.9            20.9            19.7            19.6            18.8              20            18.7            20.2            18.3            19.2            23.3            15.8            15.7            21.1            21.7            21.5              21            23.2              21            21.1            20.4            21.7            20.2            16.1             21.2              72.8             -24.3              99.6              20.7              74.5              20.4              82.3              20.6              80.8              15.9              100             4.22e-05          3.76e-05         -3.97e-05         -3.71e-05         -4.02e-05         -5.49e-05           18.3              19    
    03/27/2020 19:20:35.536       3           15.4            15.4            15.3            15.2              16            15.5            15.4            15.3            15.4            15.3            21.4            21.9            21.6            22.3            21.3            21.3            21.3            21.4            20.2            20.2            19.2            20.5            19.1            20.7            18.7            19.8            23.4            15.8            15.7            21.6            22.2            21.9            21.5            22.4            21.5            21.6            22.5            22.1            20.7            16.2             21.7              72.5             -24.3              99.6              21.2              74.4                21              81.9              21.2              80.3              15.9              100             4.25e-05          3.23e-05         -3.83e-05         -3.29e-05         -3.88e-05         -5.12e-05           18.6            19.2    
    03/27/2020 19:25:35.536       4           15.4            15.4            15.4            15.2              16            15.5            15.4            15.3            15.4            15.3            21.7            22.1            21.9            22.4            21.6            21.6            21.6            21.8            20.6            20.6            19.5              21            19.4            21.1              19            20.1            23.4            15.8            15.7            21.9            22.4            22.1            21.8            22.4            21.8              22            22.7            22.3              21            16.1               22              72.3             -24.2              99.6              21.5                74              21.4              81.5              21.5              79.9              15.9              100             3.88e-05          2.65e-05         -3.73e-05         -2.78e-05         -3.72e-05         -4.77e-05           18.9            19.3    
    03/27/2020 19:30:35.576       5           15.4            15.5            15.4            15.2              16            15.5            15.5            15.3            15.5            15.4            21.9            22.3              22            22.5            21.9            21.8            21.8              22            20.9            20.9            19.7            21.3            19.6            21.3            19.2            20.4            23.3            15.8            15.7            22.1            22.6            22.3            22.1            22.5              22            22.2            22.7            22.5            21.3            16.2             22.3              72.1             -24.1              99.5              21.8              73.9              21.6              81.2              21.8              79.7              15.9              100             3.77e-05          2.31e-05         -3.55e-05         -2.33e-05         -3.66e-05         -4.46e-05           19.1            19.5    
    03/27/2020 19:35:35.574       6           15.5            15.5            15.4            15.2              16            15.6            15.5            15.3            15.5            15.4            22.1            22.5            22.1            22.6            22.1              22            21.9            22.2            21.1            21.1            19.9            21.5            19.7            21.5            19.4            20.5            23.5            15.8            15.7            22.3            22.7            22.4            22.2            22.4            22.2            22.3            22.8            22.5            21.5            16.2             22.5                72             -24.1              99.5                22              73.8              21.8                81              21.9              79.5                16              100             3.53e-05          1.93e-05         -3.59e-05         -2.12e-05         -3.64e-05         -4.28e-05           19.2            19.6    
    03/27/2020 19:40:35.536       7           15.5            15.5            15.4            15.2            15.5            15.6            15.5            15.3            15.5            15.4            22.2            22.6            22.2            22.6            22.2              22              22            22.3            21.2            21.2              20            21.7            19.8            21.6            19.5            20.7            23.3            15.8            15.7            22.4            22.8            22.5            22.4            22.4            22.3            22.5            22.8            22.6            21.7            16.1             22.7                72             -24.1              99.4              22.2              73.7              21.9              80.7              22.1              79.3                16              100             3.47e-05          1.67e-05          -3.5e-05         -1.91e-05         -3.51e-05         -4.15e-05           19.2            19.6    
    03/27/2020 19:45:35.546       8           15.5            15.5            15.5            15.2            15.5            15.6            15.5            15.4            15.5            15.5            22.2            22.6            22.2            22.7            22.3            22.2            22.2            22.4            21.3            21.4            20.1            21.8            19.9            21.8            19.6            20.8            23.4            15.8            15.7            22.5            22.9            22.6            22.5            22.5            22.4            22.6            22.9            22.7            21.8            16.1             22.7              71.9             -24.1              99.5              22.3              73.6              22.1              80.6              22.2              79.2                16              100             3.52e-05          1.66e-05         -3.57e-05         -1.85e-05         -3.65e-05         -4.13e-05           19.3            19.6    
>> stackedplot(tt(:,1:10))

In less recent versions, you won't be able to use PreserveVariableNames, they will be modified with a warning. And you won't be able to use readtimetiable, use readtable and table2timetable.

If stackedplot isn't doing what you need, you can make whatever other plot you want with something like

plot(tt.Time,tt.Chan101_C_)

but don't use datetick on a datetime plot. For sure, don't do this:

D = data{:,2}; 
d = datenum(D);
date = datetime(d,'Format','dd-MM-yyyy HH:mm:ss.SS','convertFrom','datenum');

If the data are read in as text, convert them directly to datetime. In recent versions, read them in directly as datetimes using detectimportoptions.

[Márcio Gonçalves]

Thank you all for your answers.

I will try your suggestions as soon as possible and I give you the feedback.

My matlab version is R2019a.

Answer 2

[Márcio Gonçalves]

Dear Cris LaPierre,

Your code works perfectly. Thank you.

Dear Peter Perkins,

My matlab doesn't work with "PreserveVariableNames".

Thanks

[Peter Perkins]

As I said, "In less recent versions, you won't be able to use PreserveVariableNames, they will be modified with a warning. And you won't be able to use readtimetiable, use readtable and table2timetable." Unless you are using a really old version of MATLAB, I really, strongly, recommend that you try what I have suggested.

[Márcio Gonçalves]

ok, thank you for your help.