Findpeaks from the excel data graph

Hello Everyone,

I am trying to find the peak from the certain range on my x axis but its not working and giving me the error "Arrayindisices must be positive intergers or logical values".I am atatching the code and excel file as follow.Any help would be appreciated. Thanks in advance.

clc

Data = xlsread('test.xlsx');

%% Step 2 data

x2 =Data(655:8466,6); % Sample temprature

y2 =Data(655:8466,3); % Umsubstracted temprature

figure

plot(x2,y2);

set(gca,'ydir', 'reverse')

title('Step 2 Data')

hold on

%% Peak for step 2

J = x2(x2>90 & x2<120);

[pks, locs] = findpeaks((x2(J)),'Npeaks',1)

Answer 1

[Star Strider]

To create a logical vector for ‘J’, just do:

J = (x2>90 & x2<120);

Then the reference to it works correctly.

However there are no peaks in that region (at least that findpeaks identifies as peaks).

% C1 = readcell('https://www.mathworks.com/matlabcentral/answers/uploaded_files/632270/test123.xlsx');
T1 = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/632270/test123.xlsx','VariableNamingRule','preserve')

T1 = 24689×9 table
    Var1      Time      Unsubtracted    Baseline    Program    Sample    Approx.    Heat Flow    Uncorrected
    ____    ________    ____________    ________    _______    ______    _______    _________    ___________

    NaN            0      -1.3255          0          50       50.062       0           1          -86.659  
    NaN     0.001667      -1.3257          0          50       50.062       0           1           -86.66  
    NaN     0.003333      -1.3258          0          50       50.062       0           1           -86.66  
    NaN        0.005       -1.326          0          50       50.062       0           1           -86.66  
    NaN     0.006667       -1.326          0          50       50.066       0           1           -86.66  
    NaN     0.008333      -1.3262          0          50       50.066       0           1           -86.66  
    NaN         0.01      -1.3265          0          50       50.062       0           1           -86.66  
    NaN     0.011667      -1.3266          0          50       50.062       0           1          -86.661  
    NaN     0.013333      -1.3265          0          50       50.062       0           1           -86.66  
    NaN        0.015      -1.3267          0          50       50.062       0           1          -86.661  
    NaN     0.016667      -1.3268          0          50       50.066       0           1          -86.661  
    NaN     0.018333      -1.3269          0          50       50.066       0           1          -86.661  
    NaN         0.02      -1.3272          0          50       50.066       0           1          -86.661  
    NaN     0.021667      -1.3274          0          50       50.062       0           1          -86.661  
    NaN     0.023333      -1.3275          0          50       50.066       0           1          -86.662  
    NaN        0.025      -1.3275          0          50       50.066       0           1          -86.662  

x2 = T1{655:8466,6};           % Sample temprature 
y2 = T1{655:8466,3};           % Umsubstracted temprature 

figure 
plot(x2,y2);
set(gca,'ydir', 'reverse')
title('Step 2 Data')
hold on 

%% Peak for step 2
J = (x2>90 & x2<120);
[pks, locs] = findpeaks((x2(J))),'Npeaks',1)

pks =

  0×1 empty double column vector


locs =

  0×1 empty double column vector

.