Calculating Median Absolute Deviation in C#

Question

I am required to perform a number of statistical calculations on a number set and one of the things I need to calculate is the Median Absolute Deviation. I was supplied with an ISO standard and all it tells me is

I have no idea what to do with that info as I do not have any statistical math training. As such, I can't translate the above into a C# function.

I should add that the otherwise useful Math.Net library does NOT include the MAD function. — Captain Kenpachi, Apr 25 '17 at 12:12
Math don't have this. You need to create your own method for this. You need to have a clear algo. From them then on its a downhill journey. — Nikhil Agrawal, Apr 25 '17 at 12:15
Could *med(x)* be the median of all x? (Ie. .50th percentile.) — Richard, Apr 25 '17 at 12:16

score 5 · Accepted Answer · answered Apr 25 '17 at 12:18

5

Median is a middle element of the sorted array (or average of two middle items if the array has even items):

  double[] source = new double[] { 1, 2, 3, 4, 5 };

  Array.Sort(source);

  double med = source.Length % 2 == 0
    ? (source[source.Length / 2 - 1] + source[source.Length / 2]) / 2.0
    : source[source.Length / 2];

  double[] d = source
    .Select(x => Math.Abs(x - med))
    .OrderBy(x => x)
    .ToArray();

  double MADe = 1.483 * (d.Length % 2 == 0
    ? (d[d.Length / 2 - 1] + d[d.Length / 2]) / 2.0
    : d[d.Length / 2]);

answered Apr 25 '17 at 12:18

Dmitry Bychenko

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I am going to trust you because I like your beard. Thank you. – Captain Kenpachi Apr 25 '17 at 12:20
1

@Captain Kenpachi: instead of trusting, I'd rather run some tests ;) – Dmitry Bychenko Apr 25 '17 at 12:21
1

Of course. I do have a set of results I can compare against. – Captain Kenpachi Apr 25 '17 at 12:25

score 0 · Answer 2 · answered Apr 25 '17 at 12:17

0

Make simple steps:
1. Find median med of x[] array (you can just sort array and get middle value, but there are more effective methods)
2. Build array d[] of absolute differences with median
3. Find median of d[] array
4. Calc MADe

answered Apr 25 '17 at 12:17

MBo

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score 0 · Answer 3 · edited May 23 '17 at 12:02

0

How to program a function, which will calculate the median, you will find here

then your function can look like this

var arrOfValues = new int[] { 1, 3, 5, 7, 9 };

var di = new List<int>();  //List where all di will be stored
var median = calcMedian();  //See the link how to write it
foreach(var elem in arrOfValues)
{
   di.Add(Math.Abs(elem - median));
}

edited May 23 '17 at 12:02

Community

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answered Apr 25 '17 at 12:22

Torben

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Calculating Median Absolute Deviation in C#

3 Answers3

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