MATLAB: How to plot several curves on the same figure plot with the same StartTime

MATLABplotseveral curves

Hi guys,

again a small problem. I would like to plot several curves in one figure, but beecause it's a time series, I get a plot where the curves are behind each other.

I saw in one tutrial, that it's possible to set the StartTime to zero for both curves, but I can't find it anymore. Could you please help me?

% Read tables
C1 = readtable('Curve1.xlsx');
C2 = readtable('Curve2.xlsx');
% Convert to timetable
TTC1 = table2timetable(C1);
TTC2 = table2timetable(C2);
% Interpolate
dt = milliseconds(100);
IC1 = retime(TTC1,'regular','linear','TimeStep', dt);
IC2 = retime(TTC2,'regular','linear','TimeStep', dt);
% Plot
plot(IC1.Time, IC1.Volt);
hold on;
plot(IC2.Time, IC2.Volt);

Thanks a lot.

Best Answer

Do you mean https://www.mathworks.com/help/matlab/ref/timeseries.synchronize.html ?

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MATLAB: Importing HH:MM:SS from excel

datestr is the (old) command to create strings that represent dates and times. So that's why you have a char array. If you import as numbers, you'll get time in units of days (that how Excel stores them), and so you might see something like

>> Time
Time =
      0.04309
      0.12784
      0.21258

You have not provided enough information to go on, but as Ahmet says, since R2014b datetime and duration are probably a better choice than using datestr. One thing you might do is this:

>> d = days(Time)
d = 
   0.04309 days
   0.12784 days
   0.21258 days
>> d.Format = 'hh:mm:ss'
d = 
   01:02:03
   03:04:05
   05:06:07
>> plot(d,1:3)

MATLAB: How to get time for 50%, 90% and 100% of a graph

Only some of your records follow the model you describe.

For those that do, this works (using the code you posted to get the ‘IP1.Time’ and ‘IP1.Volt’ vectors):

Tsec = second(IP1.Time);                                                                % Convert To Seconds
Volts = IP1.Volt;                                                                       % Retrieve From Table
Voltsd = Volts - Volts(1);                                                              % Subtract Baseline Offset
VoltsL = Voltsd > 0.01;
Ix0 = find(Voltsd>0.01, 1, 'first');
fcn = @(b,x) b(1).*(1 - exp(b(2).*(x + b(3))));                                         % Model Equation
B = fminsearch(@(b) norm(Voltsd(VoltsL) - fcn(b,Tsec(VoltsL))), [1; -0.5; Tsec(Ix0);]); % Estimate Parameters
T50  = fzero(@(t) fcn(B,t) - 0.5*B(1), 1)                                               % Time At 50% Of Max
T90  = fzero(@(t) fcn(B,t) - 0.9*B(1), 1)                                               % Time At 90% Of Max
figure
plot(Tsec(VoltsL), Voltsd(VoltsL), '-')
hold on
plot(Tsec(VoltsL), fcn(B,Tsec(VoltsL)), '-r')
xl = min(xlim);
yl = min(ylim);
plot([xl T50], [1 1]*0.5*B(1),'--g', [1 1]*T50, [yl 0.5*B(1)],'--g')
plot([xl T90], [1 1]*0.9*B(1),'--c', [1 1]*T90, [yl 0.9*B(1)],'--c')
hold off
grid
xlabel('Time (s)')
ylabel('Volts')
text(T50, 0.5*B(1), sprintf('\\leftarrow 50%%: %4.1fV, %4.1fs', 0.5*B(1), T50), 'HorizontalAlignment','left', 'VerticalAlignment','middle')
text(T90, 0.9*B(1), sprintf('\\leftarrow 90%%: %4.1fV, %4.1fs', 0.9*B(1), T90), 'HorizontalAlignment','left', 'VerticalAlignment','middle')

Append my code to the code you posted to use it. I had to extract the times as seconds in order for the regression to work. It appears to g1ve good results, and estimates the time delay to onset (as ‘B(3)’) as well.

How to get time for 50%, 90% and 100% of a graph - 2019 07 19.png

Make appropriate changes to get the results you want.

Best Answer

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MATLAB: How to get time for 50%, 90% and 100% of a graph

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