Find Time when two conditions are met in two colomns

I have data set

Colomn 1= Time in micro seconds

Colomn 2 = Negative voltage

Colomn 3 = Out put current pulse

(1) How to get Time when Current is 50% after max negative voltage is applied BEFORE peak Current (MAX)

(2) How to get Time when Current is 50% after max negaitve voltage is applied AFTER Peak Current (MAX)

clear

data =load('Data1.txt');

Time=data(:,1);

Voltage=data(:,2);

Current=data(:,3);

Answer 1

[dpb]

Really don't need the applied signal at all to answer the Q?...

data=load('Data1.txt');
[Imx,iImx]=max(data(:,3));                      % find, locate peak
ixRise=find(data(:,3)>=Imx/2,1,'first');        % and rise and
ixFall=find(data(:,3)>=Imx/2,1,'last');         % fall locations...

The above has the granularity of the sampling rate; you could also then use interp1 intersection to get and find the actual intersection if that much precision is needed.

fmt="Peak time (msec): %.1f, Max I: %.3f\n50%% TRise (msec): %.1f  TFall(msec): %.1f\n";
>> fprintf(fmt,data(iImx,1)*1E6,Imx, data(ixRise,1)*1E6, data(ixFall,1)*1E6)
Peak time (msec): 39.6, Max I: 59.474
50% TRise (msec): 18.6  TFall(msec): 41.2

>> (maxk(data(:,3),10))  % Inspect peak current area --
ans =
   59.4738
   57.0392
   57.0392
   57.0392
   57.0392
   56.6914
   56.3436
   56.3436
   56.3436
   56.3436
>> 

One might consider using an average or smoothing instead of the one-point maximum above...for at least this dataset, there are five values at the plateau with just the one spike that is the actual peak max that may well be tied in with the change in input? That's a little more involved, but above gives the idea.

plot(data(:,1),[data(:,2)/100 data(:,3)])       % scale applied signal to be able to see detail easily
ylim([-20 70])                                  % and set appropriate y range
yline(Imx/2,'r:','HalfMax');
plot(data(ixRise,1),Imx/2,'r*')
plot(data(ixFall,1),Imx/2,'r*')

Of course, should plot and examine first before doing anything...above yields

[Akhtar Rind]

Thanks, I am just begnner. Please show me how you do this

Not getting this, where do you defined ixRise?

fmt="Peak time (msec): %.1f, Max I: %.3f\n50%% TRise (msec): %.1f TFall(msec): %.1f\n";

>> fprintf(fmt,data(iImx,1)*1E6,Imx, data(ixRise,1)*1E6, data(ixFall,1)*1E6)

Peak time (msec): 39.6, Max I: 59.474

50% TRise (msec): 18.6 TFall(msec): 41.2

[dpb]

Oh, sorry...trimmed too much in cleaning up for neatness...

See Ammended Answer for "the rest of the story!"

[Akhtar Rind]

Fantastic. This is working. One more query related to above data.

How can we get Time when voltage is reached 980V.

Actual point is 980 but there is some overshoot as well but I want time when Voltage is 980V.

[dpb]

Same idea -- but be aware there may not be an exact match to a floating point number so using "==" in find is somewhat risky. ismembertol solves a lot of those kinds of issues pretty simply.

As above, you return the index and look up time from it...