median of grouped frequency data
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Given the data below
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1712751/image.png)
calculate the median of the data in MATLAB
I have the code below
class_intervals = [420 430; 430 440; 440 450; 450 460; 460 470; 470 480; 480 490; 490 500];
frequencies = [336, 2112, 2336, 1074, 1553, 1336, 736, 85];
% Calculate the cumulative frequencies
cum_frequencies = cumsum(frequencies)
% Calculate the total number of observations
N = sum(frequencies);
% Find the median class (where cumulative frequency exceeds N/2)
median_class_index = find(cum_frequencies >= N/2, 1)
% Extract the lower boundary, frequency, and cumulative frequency of the class before the median class
L = class_intervals(median_class_index, 1) % lower boundary of the median class
f = frequencies(median_class_index) % frequency of the median class
if median_class_index == 1
cf = 0; % cumulative frequency before the median class
else
cf = cum_frequencies(median_class_index - 1) % cumulative frequency before the median class
end
% Calculate the width of the median class interval
h = class_intervals(median_class_index, 2) - class_intervals(median_class_index, 1)
% Calculate the median using the formula
median = L + ((N/2 - cf) / f) * h
However I was wondering if instead of calculating it manually is there any inbuilt function in MATLAB to calculate median of grouped data.
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Answers (1)
Anurag Ojha
on 11 Jun 2024
Hi Nafisa
You can use 'grpstats' function in order to calculate median of a grouped data. Adding a pseudo code:
% Create a table with the class intervals and frequencies
data = table(class_intervals, frequencies, 'VariableNames', {'ClassIntervals', 'Frequencies'});
% Calculate the median using grpstats
median_data = grpstats(data, [], 'median', 'DataVars', 'ClassIntervals');
% Extract the median values
median_values = median_data.median_ClassIntervals;
% Display the median values
disp(median_values)
There is also a inbuilt 'Median' function that you can use to caluclate median.
data = [10, 20, 30, 40, 50];
median_value = median(data);
disp(median_value);
Adding documentation link for your reference:
5 Comments
Anurag Ojha
on 13 Jun 2024
Edited: Anurag Ojha
on 13 Jun 2024
Hi Nafisa
I am not getting this error at my end when I execute the provided code. Can you please provide the exact code that you are executing which results in this error.
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