How to create a matrices using while loop?

Hi,

I am creating a 6x3 matrices using while loop with the variable increments by 1 (increment=1:1:5). My codes seems to work but it shows one row of the result at a time, instead of creating a matrices with 6 rows and 3 columns in the command window.

>> r=0.1;
y=2.5;
i=0;
while i<=5
    i=i+1;
    dis(i)=r.*sin(y.*i);
    tim(i)=dis(i)*2;
    a=[i dis(i) tim(i)]
end

a =
    1.0000    0.0598    0.1197
a =
    2.0000   -0.0959   -0.1918
a =
    3.0000    0.0938    0.1876
a =
    4.0000   -0.0544   -0.1088
a =
    5.0000   -0.0066   -0.0133
a =
    6.0000    0.0650    0.1301

Instead of having my answer a=, how do i put them into matrix array (6x3) as the increments increases by 1 until it hits 5 using while loop only?

Thank you,

Answer 1

[Stephen23]

r = 0.1;
y = 2.5;
i = 0;
a = []; % <---
while i<=5
    i=i+1;
    dis = r.*sin(y.*i);
    tim = dis*2;
    a = [a;i,dis,tim];
    %    ^^
end
display(a)

a = 6×3

1.0000 0.0598 0.1197 2.0000 -0.0959 -0.1918 3.0000 0.0938 0.1876 4.0000 -0.0544 -0.1088 5.0000 -0.0066 -0.0133 6.0000 0.0650 0.1301

But this is not an efficient use of MATLAB. A much better approach is to use a FOR loop with preallocated array, e.g.:

N = 6;
a = nan(N,3);
for k = 1:N
    dis = r.*sin(y.*k);
    tim = dis*2;
    a(k,:) = [k,dis,tim];
end
display(a)

a = 6×3

1.0000 0.0598 0.1197 2.0000 -0.0959 -0.1918 3.0000 0.0938 0.1876 4.0000 -0.0544 -0.1088 5.0000 -0.0066 -0.0133 6.0000 0.0650 0.1301

Note that using a loop is not required, the simpler MATLAB approach would be something like this:

vec = 1:N;
dis = r.*sin(y.*vec);
tim = dis*2;
a = [vec;dis;tim].'

a = 6×3

1.0000 0.0598 0.1197 2.0000 -0.0959 -0.1918 3.0000 0.0938 0.1876 4.0000 -0.0544 -0.1088 5.0000 -0.0066 -0.0133 6.0000 0.0650 0.1301

[Teb Keb]

thank you, so much. It clarified lot of stuff.