How to fill a matrix with formulas

Hi

I have a matrix as follows:

I want to fill this matrix (4,5) whose first member is y (1,1) = 0.4 using the formula

y (i) = 2 * y (i-1) * (1-y (i-1))

Please write the source for me.

[John D'Errico]

This makes no sense at all. You have a 2 dimensional matrix. But you define

y(i) = 2 * y(i-1) * (1-y(i-1))

So a function of only ONE index.

[aziz monavar]

I understand. So it is not possible to write code that uses this formula to change zero members?

Answer 1

[William Rose]

@aziz monavar,

I see from your comment that you want the transpose. Therefore do this:

y=zeros(1,20);
y(1)=0.4;
for i=2:20, y(i)=2*y(i-1)*(1-y(i-1)); end
y=reshape(y,[4,5])';
disp(y) 

    0.4000    0.4800    0.4992    0.5000
    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000

Try.

[aziz monavar]

@William Rose

no, I do not mean this

I want my output matrix to be a 4x5 matrix but you have given a 5x4 matrix as output.

y=zeros(1,20);
y(1)=0.7;
for i=2:20  
y(i)=1.3*y(i-1)*(1-y(i-1));
end
y=reshape(y,[4,5]);
disp(y)

    0.7000    0.2430    0.2335    0.2314    0.2309
    0.2730    0.2391    0.2327    0.2312    0.2309
    0.2580    0.2365    0.2321    0.2311    0.2308
    0.2489    0.2348    0.2317    0.2310    0.2308

My desired matrix:

y_answer =
0.7000  	0.2730  	0.2580  	0.2489  	0.2430
0.2391  	0.2365  	0.2348  	0.2335  	0.2327
0.2321  	0.2317  	0.2314  	0.2312  	0.2311
0.2310  	0.2309  	0.2309  	0.2308  	0.2308

I want to give y_answer as outputIn other words, from the first member to the fifth member of the y matrix, fill in the first row of the matrix and also the next rows of the matrix.

Answer 2

[William Rose]

@aziz monavar,

You have a matrix y(i,j) but your formula is only for y(i). That is the problem @John D'Errico identifies.

If you want to treat your 4x5 matrix as if it were 1x20, you can apply your formula, and then reshape the vector to a 4x5 matrix. The code to do it is

y=zeros(1,20);
y(1)=0.4;
for i=2:20
    y(i)=2*y(i-1)*(1-y(i-1));
end
y=reshape(y,[4,5]);
disp(y)

    0.4000    0.5000    0.5000    0.5000    0.5000
    0.4800    0.5000    0.5000    0.5000    0.5000
    0.4992    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000    0.5000

Try it.

[aziz monavar]

This is the right code for me, thank you, but it is a problem that I explained in the following example

>> y

y =

     1     5     3     2     7     6     5     8     9    10    11    12    13    14    15    16

>> reshape(y,[4,4])

ans =

     1     7     9    13
     5     6    10    14
     3     5    11    15
     2     8    12    16

>> y_answer

y_answer =

     1     5     3     2
     7     6     5     8
     9    10    11    12
    13    14    15    16

"y_answer" is my answer, but "reshape" puts a column in the matrix. You can give a code that is arranged like "y_answer".