What do the codes in line 9 and 10 do in the program?

clc; close all; clear all;
n1=0:4;
x1=[0 1 2 3 4]; %given first sequence
n2=-2:2;
x2=[2 2 2 2 2]; %given second sequence
n=min(min(n1),min(n2)):max(max(n1),max(n2));
y1=zeros(1,length(n));
y2=y1;
y1(find((n>=min(n1))&(n<=max(n1))==1))=x1;              % What does this do?
y2(find((n>=min(n2))&(n<=max(n2))==1))=x2;              % What does this do?
y=y1+y2;  %addition of the two given sequences
subplot(1,1,1);
stem(n,y);
title('Addition of the two given sequences.');

Above is a program given by my professor to perform addition of two Discrete signals in MATLAB. I've understood what every line of the program does except the two lines shown below

y1(find((n>=min(n1))&(n<=max(n1))==1))=x1;              % What does this do?
y2(find((n>=min(n2))&(n<=max(n2))==1))=x2;

Can someone please tell me what exactly do these lines do in the program and what is the logic of it?

Thank you

Answer 1

[Fifteen12]

This is using logical indexing to filter out specific numbers. This code is selecting all the indices in y1 that correspond to the same indices in n where n not within the range of n1 (<= to n1's minimum and >= n1's maximum). Then it's setting all these indices equal to the values in x1. Broken down step by step you get:

n = 3:7;
n1 = [4, 5, 6];
x1 = 5;

A = min(n1)

A = 4

B = max(n1)

B = 6

C = (n >= A) & (n <= B)

C = 1×5 logical array
   0   1   1   1   0

D = C == 1

D = 1×5 logical array
   0   1   1   1   0

E = find(D)

E = 1×3

2 3 4

y1(E) = x1

y1 = 1×4

0 5 5 5

It appears that setting D equal to C == 1 is redundant, as find already does that...