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Statistics for Programmers - Frequency Distributions

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source link: https://nishtahir.com/1-statistics-for-programmers-frequency-distributions/
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By Nish Tahir in Statistics For Programmers — Feb 11, 2024

Statistics for Programmers - Frequency Distributions

A Frequency Distribution is a common way to understand a trend in a dataset. It's a tabular representation of the number of times a value appears in a dataset. If we denote values in a dataset as x1,x2,…,xn, their corresponding frequencies can be denoted as f1,f2,…,fn. This relationship can be expressed as a table.

Value (x)Frequency (f)x1f1x2f2⋮⋮xnfn

Applying this practically, let's consider a dataset of 10 users who were asked to review a product on a scale of 1 to 5. The dataset can be represented as an array of reviews.

[3, 1, 5, 5, 2, 4, 5, 3, 1, 5]

We can construct a frequency distribution table for this dataset by counting the number of times each unique element appears in the array.

Value (x) | Frequency (f)
-------------------------
1         | 2
2         | 1
3         | 2
4         | 1
5         | 4

This can be expressed in code using a Map (or Dictionary depending on your language of choice) of unique values and how many times they appear in a given dataset.

Once again considering our array of reviews,

const arr = [3, 1, 5, 5, 2, 4, 5, 3, 1, 5];

We can construct a function that counts the number of times each unique element appears in the array.

function frequencyDistribution(arr) {
  const map = {};
  for(let i = 0; i < arr.length; i++) {
      const item = arr[i];
      if (map[item]) {
          map[item] += 1;
      } else {
          map[item] = 1;
      }
  }
  return map;
}

Applying this function to our dataset gives us the following output,

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