This example shows how to fit kernel distributions
to grouped sample data using the
Step 1. Load sample data.
Load the sample data.
The data contains miles per gallon (
measurements for different makes and models of cars, grouped by country
of origin (
Origin), model year (
and other vehicle characteristics.
Step 2. Group sample data by origin.
MPG data by origin (
for cars made in the USA, Japan, and Germany.
Origin = nominal(Origin); MPG_USA = MPG(Origin=='USA'); MPG_Japan = MPG(Origin=='Japan'); MPG_Germany = MPG(Origin=='Germany');
Step 3. Compute and plot the pdf.
Compute and plot the pdf for each group.
figure; [fi,xi] = ksdensity(MPG_USA); plot(xi,fi,'r-'); hold on; [fj,xj] = ksdensity(MPG_Japan); plot(xj,fj,'b-.') [fk,xk] = ksdensity(MPG_Germany); plot(xk,fk,'k:') legend('USA','Japan','Germany') title('MPG by Origin'); xlabel('MPG'); hold off;
The plot shows how miles per gallon (
performance differs by country of origin (
Using this data, the USA has the widest distribution, and its peak
is at the lowest
MPG value of the three origins.
Japan has the most regular distribution with a slightly heavier left
tail, and its peak is at the highest
of the three origins. The peak for Germany is between the USA and
Japan, and the second bump near 44 miles per gallon suggests that
there might be multiple modes in the data.