Make matrix with loop

hi i'm new I am executing the loop using FOR. Each loop I get 1 number. I want to put those numbers in a matrix.

Can anyone help me?

Answer 1

[Walter Roberson]

In the general case:

xvals = [list of x values, does not have to be regularly spaced or even sorted];
numx = length(xvals);
y = zeros(1,numx);   %pre-allocate
for xidx = 1 : numx
    x = xvals(xidx);
    thisy = some calculation involving x
    y(xidx) = thisy;
end

In the special case where x is integers increasing by 1, but not necessarily starting from 1:

firstx = value
lastx = value
numx = lastx - firstx + 1;
y = zeros(1, numx);   %pre-allocate
for x = firstx : lastx
    thisy = some calculation involving x
    y(x - firstx + 1) = thisy;
end

In the special case where x is integers starting from 1 and increasing by 1:

y = zeros(1, lastx);   %pre-allocate
for x = 1 : lastx
    thisy = some calculation involving x
    y(x) = thisy;
end

It would be common that the expression is simple enough that it is clear to put the body into one line:

y = zeros(1, lastx);   %pre-allocate
for x = 1 : lastx
    y(x) = some calculation involving x
end

pre-allocation is not strictly necessary, but it can make a fairly noticable difference in performance.

[Pham Anh]

i has a 25x2 matrix

i using this function to loop

function test(A)
Ax=A(:,1);
for i=1:size(Ax,1)
    x = Ax(i)*2+7
end

i dont know how to list the x values

My purpose is to create a 25x1 matrix from x

[Walter Roberson]

function test(A)
Ax=A(:,1);
x = zeros(size(Ax,1),1);
for i=1:size(Ax,1)
    x(i) = Ax(i)*2+7
end