Filtering out sections of a graph

The title may not be as descriptive as it should - I aplologise: still getting used to MATLAB

I am wondering if you could help me?

At the moment, I am using data obtained from the Department of Transport (RDL0103) and plotting it as stacked bar graphs.

The code I have so far is shown below (only contains inputs):

clearvars
clc
load CodingData.mat

a=Year;
data_set = (2017:1:2037);

b1=Trunk_Motorways;                                     % Major Motorways, [miles]
b2=Principle_Motorways;                                 % Minor Motorways, [miles]
b3=Total_Motorways;                                     % Total Amount of Miles Constructed on both types of motorways, [miles]

x11 = interp1(a, b1, data_set, 'linear', 'extrap')
x12 = interp1(a, b2, data_set, 'linear', 'extrap')
x13 = interp1(a, b3, data_set, 'linear', 'extrap')

c1=Trunk_A_Roads;
c2=Principle_A_Roads;
c3=Total_A_Roads;

a21 = interp1(a, c1, data_set, 'linear', 'extrap')
a22 = interp1(a, c2, data_set, 'linear', 'extrap')
a23 = interp1(a, c3, data_set, 'linear', 'extrap')

d1=B_Roads;
d2=C_Roads;
d3=U_Roads;
d4=C_And_U_Roads;

x31 = interp1(a, d1, data_set, 'linear', 'extrap')
x32 = interp1(a, d2, data_set, 'linear', 'extrap')
x33 = interp1(a, d3, data_set, 'linear', 'extrap')
x34 = interp1(a, d4, data_set, 'linear', 'extrap')

e1=All_Major_Roads;
e2=All_Minor_Roads;

x41 = interp1(a, e1, data_set, 'linear', 'extrap')
x42 = interp1(a, e2, data_set, 'linear', 'extrap')

% Stacked Graph

y=[b1 b2 b3];
bar(a,y,'stacked')

This is the results I get. My question is this:

Is it possible for me to show only certain catergories on the figure without me having to change the code (or make multiple versions of the same code)? [e.g. Showing only Trunk_Motorways and Total_Motorways but not Principle_Motorways]