# How to write in Matlab a matrix whose coefficients depend on a real alpha parameter

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Djamel el 26 de Mzo. de 2024
Comentada: Djamel el 2 de Abr. de 2024
A(i,j) = (1+alpha*x(i)*y(j))*exp(x(i)*y(j))
where almpha is a real parameter, x(i) and y(j) points in [0 , 1] with i , j = 1, ..., N
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John D'Errico el 26 de Mzo. de 2024
Editada: John D'Errico el 26 de Mzo. de 2024
Many ways. It seems unclear exactly what is your goal. And what are x and y? Are they just a list of numbers? Or a sequence as linspace would provide?
For example, you might do this:
N = 4;
x = linspace(0,1,N);
y = linspace(0,1,N);
syms alpha
A = (1+alpha*x.'*y)*exp(x.'*y)
A =
vpa(A,5)
ans =
Of course, x and y might be just any arbitrary vectors of numbers.
Another approach would be to write it as a function handle. This time I'll use random vectors for x and y.
x = sort(rand(1,N))
x = 1x4
0.0962 0.1445 0.9101 0.9192
y = sort(rand(1,N))
y = 1x4
0.0370 0.2099 0.4181 0.4717
Afun = @(alph) (1+alph*x.'*y)*exp(x.'*y);
And now we can evaluate Afun for any value of the parameter.
Afun(0.3)
ans = 4x4
4.1115 4.5130 5.0803 5.2430 4.1284 4.5323 5.1030 5.2666 4.3969 4.8383 5.4627 5.6418 4.4000 4.8419 5.4670 5.6462
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Djamel el 2 de Abr. de 2024
Thank you so much John D'Errico. Both script suggestions work.

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### Más respuestas (1)

Voss el 26 de Mzo. de 2024
Here's an example:
alpha = 0.4;
N = 9;
x = linspace(0,1,N);
y = linspace(0,1,N);
xy = x(:).*y(:).' % column x * row y
xy = 9x9
0 0 0 0 0 0 0 0 0 0 0.0156 0.0312 0.0469 0.0625 0.0781 0.0938 0.1094 0.1250 0 0.0312 0.0625 0.0938 0.1250 0.1562 0.1875 0.2188 0.2500 0 0.0469 0.0938 0.1406 0.1875 0.2344 0.2812 0.3281 0.3750 0 0.0625 0.1250 0.1875 0.2500 0.3125 0.3750 0.4375 0.5000 0 0.0781 0.1562 0.2344 0.3125 0.3906 0.4688 0.5469 0.6250 0 0.0938 0.1875 0.2812 0.3750 0.4688 0.5625 0.6562 0.7500 0 0.1094 0.2188 0.3281 0.4375 0.5469 0.6562 0.7656 0.8750 0 0.1250 0.2500 0.3750 0.5000 0.6250 0.7500 0.8750 1.0000
A = (1+alpha.*xy).*exp(xy)
A = 9x9
1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0221 1.0446 1.0676 1.0911 1.1150 1.1395 1.1644 1.1898 1.0000 1.0446 1.0911 1.1395 1.1898 1.2422 1.2967 1.3534 1.4124 1.0000 1.0676 1.1395 1.2157 1.2967 1.3826 1.4738 1.5706 1.6732 1.0000 1.0911 1.1898 1.2967 1.4124 1.5377 1.6732 1.8199 1.9785 1.0000 1.1150 1.2422 1.3826 1.5377 1.7088 1.8976 2.1058 2.3353 1.0000 1.1395 1.2967 1.4738 1.6732 1.8976 2.1499 2.4335 2.7521 1.0000 1.1644 1.3534 1.5706 1.8199 2.1058 2.4335 2.8089 3.2385 1.0000 1.1898 1.4124 1.6732 1.9785 2.3353 2.7521 3.2385 3.8056
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