Why is NaN returned when I have all necessary input data?

I have a large data set contained in a text file that I am attempting to analyze the difference in frequency of the signal. In the following approach I am simply computing the distance between each peak. the code I have written does not throw any errors, but it doesn'ty actual return any values, either. I have been messing with it for a while and it doesn't make any sense why it would not run correctly. Does anyone see my mistake?

data1 = 'time0.txt';
opts = detectImportOptions(data1);
opts = setvaropts(opts,opts.VariableNames(1),'InputFormat','MM/dd/uuu HH:mm:ss.SSSSSS');
data = readtable(data1,opts);
data.Properties.VariableNames = {'Time','Response'};
data.Time = data.Time - data.Time(1);
data.Time.Format = 'mm:ss.SSSSSS';

% t0 = data(:,1);
% t0 = table2array(t0);
% t0 = seconds(t0);
y0 = data(:,2);
y0 = table2array(y0);
[pks,locs]=findpeaks(y0,"MinPeakProminence",2)

pks =

  0×1 empty double column vector


locs =

  0×1 empty double column vector

Average0 = mean(diff(locs))

Average0 = NaN

Answer 1

[Stephen23]

"Does anyone see my mistake?"

Your data has a range of approx 0.166: how many peaks do you expect to get with minimum peak prominence >2 (as you specified), when the data actually has a range less than a tenth of that?

fnm = 'time0.txt';
opt = detectImportOptions(fnm, 'Delimiter','\t');
opt = setvaropts(opt, 1, 'InputFormat','M/d/y H:m:s.SSSSSS');
tbl = readtable(fnm,opt);
tbl.Properties.VariableNames = {'Time','Response'}

tbl = 21000×2 table
              Time               Response
    _________________________    ________

    4/12/2023 15:42:59.575769     0.17703
    4/12/2023 15:42:59.575819     0.13004
    4/12/2023 15:42:59.575869    0.086921
    4/12/2023 15:42:59.575919    0.047983
    4/12/2023 15:42:59.575969    0.045087
    4/12/2023 15:42:59.576018    0.075336
    4/12/2023 15:42:59.576069     0.12747
    4/12/2023 15:42:59.576119     0.16737
    4/12/2023 15:42:59.576169     0.18539
    4/12/2023 15:42:59.576219     0.16866
    4/12/2023 15:42:59.576269     0.13745
    4/12/2023 15:42:59.576319    0.091105
    4/12/2023 15:42:59.576369    0.051523
    4/12/2023 15:42:59.576419    0.041225
    4/12/2023 15:42:59.576469    0.079198
    4/12/2023 15:42:59.576519     0.11653

tbl.Dur = tbl.Time - tbl.Time(1); % what is this used for?
tbl.Dur.Format = 'hh:mm:ss.SSSSSSS'

tbl = 21000×3 table
              Time               Response          Dur       
    _________________________    ________    ________________

    4/12/2023 15:42:59.575769     0.17703    00:00:00.0000000
    4/12/2023 15:42:59.575819     0.13004    00:00:00.0000499
    4/12/2023 15:42:59.575869    0.086921    00:00:00.0000999
    4/12/2023 15:42:59.575919    0.047983    00:00:00.0001499
    4/12/2023 15:42:59.575969    0.045087    00:00:00.0001999
    4/12/2023 15:42:59.576018    0.075336    00:00:00.0002499
    4/12/2023 15:42:59.576069     0.12747    00:00:00.0003000
    4/12/2023 15:42:59.576119     0.16737    00:00:00.0003500
    4/12/2023 15:42:59.576169     0.18539    00:00:00.0004000
    4/12/2023 15:42:59.576219     0.16866    00:00:00.0004500
    4/12/2023 15:42:59.576269     0.13745    00:00:00.0005000
    4/12/2023 15:42:59.576319    0.091105    00:00:00.0005500
    4/12/2023 15:42:59.576369    0.051523    00:00:00.0006000
    4/12/2023 15:42:59.576419    0.041225    00:00:00.0006499
    4/12/2023 15:42:59.576469    0.079198    00:00:00.0007000
    4/12/2023 15:42:59.576519     0.11653    00:00:00.0007500

[pks,locs] = findpeaks(tbl.Response)

pks = 2311×1

0.1854 0.1893 0.1802 0.1841 0.1880 0.1835 0.1867 0.1825 0.1835 0.1770

locs = 2311×1

9 18 28 36 46 54 63 73 81 90

min(tbl.Response)

ans = 0.0322

max(tbl.Response)

ans = 0.1986

Answer 2

[Cris LaPierre]

Because no peaks were identified in your signal. It would appear the setting in findpeaks are not appropriate for your signal.

data1 = 'time0.txt';
opts = detectImportOptions(data1);
opts = setvaropts(opts,opts.VariableNames(1),'InputFormat','MM/dd/yyyy HH:mm:ss.SSSSSS');
data = readtable(data1,opts);
data.Properties.VariableNames = {'Time','Response'};
data.Time = data.Time - data.Time(1);
data.Time.Format = 'mm:ss.SSSSSS';

plot(data,"Time","Response")

So while there is nothing wrong with your code, you likely need to adjust your settings. I would suggest doing this interactively in a live script using the Find Local Extrema live task. You will be able to immediately see the results and, once you have find the correct settings, obtain the corresponding code if desired.