How can I replace random elements of a matrix with some definite respective values in a single line command?

I can replace a single element of a matrix. Or change multiple elements in an arithmetic series like 1st, 3rd, 5th element of a matrix with respective numbers. Or even a range of elements like 1st to 5th. But I want to randomly replace some elements with some numbers by one single line command. Like 1st, 2nd, 5th, 8th, 9th, 11th element of a matrix. Is it possible to do that with a single line code?

A=[1 2 3;4 5 6;7 8 9]

A(1)=10

A(2)=11

A(3)=12

Or

A(1:5)=[10, 11, 12, 13, 14]

A(1:2:5)=[10, 11, 12]

But don't know how to do the last thing I mentioned. Looking for help.

[Dyuman Joshi]

"But I want to randomly replace some elements with some numbers by one single line command. Is it possible to do that with a single line code?"

If I understand you correctly, it is -

A = magic(5)

A = 5×5

17 24 1 8 15 23 5 7 14 16 4 6 13 20 22 10 12 19 21 3 11 18 25 2 9

A([1 8 13 22]) = [-4 -2 0 69]

A = 5×5

-4 24 1 8 15 23 5 7 14 69 4 -2 0 20 22 10 12 19 21 3 11 18 25 2 9

[Walter Roberson]

@Al Naif comments to @Dyuman Joshi

It was really helpful

Answer 1

[Star Strider]

You are using ‘’inear indexing, and that will definitely work, although I am not certain what you want to do.

For a full explanation, see Matrix Indexing and the sub2ind and ind2sub functions to understand how they work and what they do.

A=[1 2 3;4 5 6;7 8 9] 

A = 3×3

1 2 3 4 5 6 7 8 9

A(1)=10 

A = 3×3

10 2 3 4 5 6 7 8 9

A(2)=11 

A = 3×3

10 2 3 11 5 6 7 8 9

A(3)=12

A = 3×3

10 2 3 11 5 6 12 8 9

A=[1 2 3;4 5 6;7 8 9] 

A = 3×3

1 2 3 4 5 6 7 8 9

A(1:6)=[10, 11, 12, 13, 14, 15] 

A = 3×3

10 13 3 11 14 6 12 15 9

A=[1 2 3;4 5 6;7 8 9] 

A = 3×3

1 2 3 4 5 6 7 8 9

A(1:2:5)=[10, 11, 12]

A = 3×3

10 2 3 4 12 6 11 8 9

.

Answer 2

[Voss]

"I want to randomly replace some elements with some numbers by one single line command"

A=[1 2 3;4 5 6;7 8 9];

n = 6;                     % number of elements to replace

idx = randperm(numel(A),n) % indices of elements to be replaced with new values  

idx = 1×6

8 1 4 5 3 7

val = rand(1,n)            % new values

val = 1×6

0.0840 0.0074 0.4788 0.8361 0.8203 0.0097

A(idx) = val              % perform the replacement

A = 3×3

0.0074 0.4788 0.0097 4.0000 0.8361 0.0840 0.8203 8.0000 9.0000

A=[1 2 3;4 5 6;7 8 9];

% one-line version:
A(randperm(numel(A),6)) = rand(1,6);

[Dyuman Joshi]

Modify this

idx = randperm(numel(A));
idx = idx(1:n);

to -

idx = randperm(numel(A),n);

and eliminate subsref() and substruct()

A(randperm(numel(A),n)) = rand(1,6);

[Voss]

Very good.