highlight different data on the same graph

I create a plot with two different axes

figure 
yyaxis left
plot(Tclean.x,Tclean.Temperature,'b-')
ylabel('°t')
yyaxis right
plot(Tclean.x,Tclean.ph,'r-')
ylabel('ph')

Datas come from a table that include temperature, DO and x is a time vector ('2021-07-21 02:10:00' - Format: yyyy-MM-dd HH:mm:ss).

x axis start at 2021-07-21 00:00:00 and it ends at 2021-07-23 08:40:00.

I'd like to highlight a period (from 2021-07-21 02:10:00 to 2021-07-21 08:40:00) on the same graph with a different line.

I thought to creat a loop

hold on
for i = {'2021-07-21 02:10:00'}:{'2021-07-21 08:40:00'}
    plot(Tclean.x(i),Tclean.Temperature,'bo')
end

but the output is

%Undefined function 'colon' for input arguments of type 'cell'

Answer 1

[Star Strider]

Try something like this:

Tclean = table(datetime('2021-07-21 00:00:00')+minutes(0:10:1000).', 'VariableNames',{'Time'}); % Create Table
Tclean = [Tclean array2table(rand(height(Tclean), 4))]                                          % Create Table

Tclean = 101×5 table
            Time              Var1         Var2        Var3        Var4  
    ____________________    _________    ________    ________    ________

    21-Jul-2021 00:00:00    0.0044181      0.5574     0.32765     0.63126
    21-Jul-2021 00:10:00      0.14299     0.73893    0.013102     0.33047
    21-Jul-2021 00:20:00      0.24177     0.80681     0.36718     0.44688
    21-Jul-2021 00:30:00      0.79409     0.56831     0.12128     0.73734
    21-Jul-2021 00:40:00      0.75651     0.66069    0.085325     0.11528
    21-Jul-2021 00:50:00      0.84837     0.78757     0.31821     0.47127
    21-Jul-2021 01:00:00      0.67077     0.55255     0.21959     0.49633
    21-Jul-2021 01:10:00      0.69986    0.066311     0.51486    0.049543
    21-Jul-2021 01:20:00      0.59055     0.95615      0.3558     0.51653
    21-Jul-2021 01:30:00      0.15497     0.30912     0.34082     0.31738
    21-Jul-2021 01:40:00      0.17349     0.28567    0.030185     0.33982
    21-Jul-2021 01:50:00      0.78942     0.33723     0.67319    0.098763
    21-Jul-2021 02:00:00      0.50649     0.50497     0.20147     0.12196
    21-Jul-2021 02:10:00     0.047334     0.53594     0.27033    0.087125
    21-Jul-2021 02:20:00      0.94278     0.44081     0.78531     0.23972
    21-Jul-2021 02:30:00      0.21584     0.51009     0.65319     0.20165

iv = [datetime('2021-07-21 02:10:00') datetime('2021-07-21 08:40:00')]                          % Limits

iv = 1×2 datetime array
   21-Jul-2021 02:10:00   21-Jul-2021 08:40:00

TcleanVct = (Tclean{:,1} >= iv(1)) & (Tclean{:,1} <= iv(2));                                    % Logical Vector

figure
plot(Tclean{:,1}, Tclean{:,2}, '-b')
hold on
plot(Tclean{TcleanVct,1}, Tclean{TcleanVct,2}, '--r')
hold off
grid

Make appropriate changes toi get the result you want.

.

Answer 2

[Adam Danz]

It looks like you're using datetime values and if you're not, you should be. Datetime values are not represented by strings. A datetime loop loops through days but your interval is less than a day so it will only execute for the first datetime value. Were you expected it to loop through hours / minutes / or seconds?

Why not just add a colored rectangled that spans the vertical extent of the plot between your selected dates? That will avoid precision errors.

dt = datetime('2021-07-21') + hours(0:24);
data = rand(2,numel(dt)); 
figure()
yyaxis left
h1 = plot(dt, data(1,:), 'o','DisplayName','LeftData');
yyaxis right
h2 = plot(dt, data(2,:), 'o', 'DisplayName', 'RightData');

interval = datetime({'2021-07-21 02:10:00','2021-07-21 08:40:00'});
yyaxis left
hold on
ax = gca(); 
ph = patch([interval,fliplr(interval)], ax.YLim([1 1 2 2]), 'k', ...
    'FaceAlpha', .1, 'EdgeColor','none', 'DisplayName','Selection'); 

legend([h1,h2,ph],'Location','SouthOutside', 'orientation','horizontal')