Why is my function giving me the wrong output?

I was asked to write a function finding median and mean of an array without using the built in functions or the sum function. I think my code is very close to being correct, however I am confused as to why it is giving me the output zero when it should be giving me a 3. The array I tested it with was [5 8 9 1 0 2 3 1 9]. I then tried to sort it in ascending order and index it to find the median value. When I hover the cursor over the line

medianValue = sortedArray(medianIndex);

it shows the array as sorted. So basically, I don't know why my medianValue = 0 when it should equal 3. I think that part of my function is correct because it should be indexing the sorted array at the value for medianIndex, which is 5. So it should be returning the value 3.

   function [meanValue, medianValue] = statsFunction(array)
   %function to calculate median and mode values of an array

   sortedArray = sort(array, 'ascend');
   numElements = numel(sortedArray);

   if mod(numElements, 2) ~= 0

   medianIndex = (numElements+1)/2;
   medianValue = sortedArray(medianIndex);

   else
    medianIndex1 = numElements/2;
    medianIndex2 = (numElements+1)/2;

    medianValue = (medianIndex1 + medianIndex2) / numElements;

end

    sumx = 0;
    k = 1;
    while  k <= length(array)
    sumx = sumx + array(k);
    k = k+1;

 end

    meanValue = sumx/(length(array));

[Star Strider]

When I run the if block in your code, it gives the correct result for the median. I cannot reproduce the error you report.

[Stephen23]

See also the earlier question:

https://www.mathworks.com/matlabcentral/answers/383819-how-to-use-any-size-array-as-an-input

Answer 1

[Steven Lord]

Are you sure that this is failing for an odd length input array and not an even length input array? The else branch of your if statement doesn't index into sortedArray at all, while the if branch does.

Answer 2

[Kristen O'Mara]

Thanks everyone, I fixed the issue. I needed to change the line medianValue to

     medianValue = (array(medianIndex1) +  array(medianIndex2))/2;