How to use indices in A matrix while conditonal and for loop condtion?

How to use indices in LHS of A matrix while using for and if, esleif and else condtions?

clc
clear all
m=5;n=7; A=zeros(m,m);
for j=1:n
    if j=1
        for i=1:m,
            if i==1
                A(?)=i+j
            elseif i==m 
                A(?)=i-j
            else 
                A(?)=i
            end
        end
    else
        for i=1:m,
            if i==1
                A(?)=2i+j
            elseif i==m 
                A(?)=i*j
            else 
                A(?)=j
            end
        end
    end
end

[KSSV]

It is better to explain what you are expecting out of A?

Answer 1

[Bhanu Prakash]

Hi Gayathri,

As per my understanding, you want to know how to index into the matrix "A" while using loops.

Please look at the following code, for your reference:

clc
clear all
A=zeros(3);
k=1;
for i=1:3  
    for j=1:3        
        A(i,j)=k;        
        k=k+1;        
    end    
end

In the code shown above, the indexing is done using two indices "(i,j)", where “i” represents the row number and “j” represents the column number. The resulting matrix "A" is as follows:

A =

1     2     3

4     5     6

7     8     9

This indexing can also be done using a single index "i" in the following way:

clc
clear all
A=zeros(3); 
k=1;
for i=1:9  
    A(i)=i; 
end 

The resulting matrix "A" is as follows:

A =

1     4     7

2     5     8

3     6     9

Note that, both the resulting matrices are not identical. One matrix is the transpose of the other.

You can refer to the documentation on "Array Indexing", for more info:

Array Indexing - MATLAB & Simulink - MathWorks India

Hope this answer helps you.

Thanks,

Bhanu Prakash.

Answer 2

[Raghvi]

Hey Gayathri,

I have made some edits in the code to remove errors. You can use the syntax A(i,j) to access the ith row and jth column of the matrix A.

m=5;n=7; 
A=zeros(n,m);
for j=1:n
    if j==1
        for i=1:m
            if i==1
                A(i,j)=i+j;
            elseif i==m 
                A(i,j)=i-j;
            else 
                A(i,j)=i;
            end
        end
    else
        for i=1:m
            if i==1
                A(i,j)=2*i+j;
            elseif i==m 
                A(i,j)=i*j;
            else 
                A(i,j)=j;
            end
        end
    end
end