Recording variables that satisfy a condition

Typical new matlab user here, so just looking for help and to learn, I know this is probably a simple question.

Basically, I have three variables X, Y, and Z that span from 0 to 1 spaced by 100. I want to record all instances where X + Y + Z = 1. This is what I have so far:

X = linspace(0,1,100);
Y = linspace(0,1,100);
Z = linspace(0,1,100);

poss = zeros(1000,3); %just a space to populate answers
for i = 1:100
    for j = 1:100
        for k = 1:100
            p = X(i)+Y(j)+Z(k);
            if p==1
                poss(i,1)=X(i);
                poss(i,2)=Y(j);
                poss(i,3)=Z(k);
            end
        end
    end
end

Am I on the right track? I just want to record the three variables X, Y, and Z in three columns if their sum totals to one. This is part of a more complex problem but I tried to simplify it. Thanks

[Stephen23]

"Am I on the right track?"

Probably not, unless as a self-declared "new matlab user" you already have a good practical understanding of binary floating point numbers. The answers below also do not take into account floating point error, e.g. madhan ravi's answer does not include this combination (and many others):

V = linspace(0,1,100);
V(2)

ans = 0.0101

V(98)

ans = 0.9798

1-V(2)-V(2)-V(98)

ans = 1.1102e-16

Given the essentially arbitrary rounding of these floating point sums, the task of selecting only those that happen to add to exactly one does not seem to be very meaningful. Or are you performing some floating point magic?

[madhan ravi]

Yes, thanks Stephen for the explanations.

Answer 1

[madhan ravi]

X = linspace(0,1,100);
Y = linspace(0,1,100);
Z = linspace(0,1,100);
[XX, YY, ZZ] = meshgrid(X, Y, Z);
XYZ = XX + YY + ZZ;
Pass(:, 3) = ZZ(XYZ == 1);
Pass(:, 2) = YY(XYZ == 1);
Pass(:, 1) = XX(XYZ == 1);
Pass

Pass = 4842×3

0 1.0000 0 0.0101 0.9899 0 0.0202 0.9798 0 0.0303 0.9697 0 0.0404 0.9596 0 0.0505 0.9495 0 0.0606 0.9394 0 0.0707 0.9293 0 0.0808 0.9192 0 0.0909 0.9091 0

Answer 2

[David Hill]

[x,y,z]=meshgrid(X,Y,Z);
k=x+y+z;
idx=find(k==1);