MATLAB: ‘Array indices should be positive’ error

array indices;

Let's say I'm taking an array of values from an Excel file,

maybe the first column in the excel file and I wanna find the standard deviation for it.

So the code is gonna be

col=a(:,1);

std=std(col);

It gives an output for the first run, but when I run it second time, it gives an error saying,"Array indices should be positive". Why?

Kindly help.

Thanks,

Vinisha.

Best Answer

This is the reason:

std=std(col);

You ‘overshadowed’ the std function by naming your variable ‘std’.

Do this and the problem will go away:

StDev = std(col);

You will have to change that variable in the rest of your code, however the MATLAB Editor should make that easy.

Related Solutions

MATLAB: How to calculate standard deviation of 1D array

1. You most likely have a variable named std. This command should give you that information (copy-paste it to the Command Window and run it):

which std -all

If you have a Windows computer, all those results should be in the C:\Program Files\MATLAB\... directories, and none in your user files or as variables.

2. The std function takes the standard deviation across the columns (or rows) of an array, producing one value for each column (or row). The std2 function takes the standard deviation of all the elements in the array, as though they were all a single vector.

MATLAB: Why showing ‘Array indices must be positive integers or logical values.’

m2 = zeros(N,1);                 %2Matrix of second moment matrix
    m2_pul = zeros(N,1);  %x(n)x(n+t)Matrix frame
    fs = 50;
    f = (0:N-1)/fs ; 
    for  t1 = 1:length(f)
          n = 1:N;
            m2_pul(n) = sig(n) .* sig(n+t1);       %x(n)x(n+t)
        
        m2(t1+1) = mean(m2_pul);                        %E[x(n)x(n+t)]
        m2_pul = zeros(N,1);
    end

The indices of array in MATLAB cannot be zero, negative and fractions. When you take:

    t1 = (0:N-1)/fs

t1 has fractions, you cannot use them as indices; so error.

Best Answer

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MATLAB: How to calculate standard deviation of 1D array

MATLAB: Why showing ‘Array indices must be positive integers or logical values.’

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