two variables with known values in equations; use loop in matlab

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Norzuria Ibrahim
Norzuria Ibrahim 2015-9-29
评论： Norzuria Ibrahim 2015-9-29
Hi I have question to ask. I have 3 variables with known variables, x, y, z.
x= 3, 1 , 4, 2, 1
y=3,4 ,5,1,1
z=2,2,1,2,2
I need to apply those variables in two related equations
d=x+y+2z
e=2d+xyz
how to solve this using loop
what I did
x=[3 1 4 2 1];
y=[3 4 5 1 1];
z=[2 2 1 2 2];
for i=1:length(x);
j=1:length(y);
k=1:length(z);
d=x(i)+y(j)+2*z(k)
d=d+1
e=2*d+(x(i)*y(j)*z(k))
end
did not work

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采纳的回答

Andrei Bobrov
Andrei Bobrov 2015-9-29
x=[3 1 4 2 1];
y=[3 4 5 1 1];
z=[2 2 1 2 2];
d=x+y+2*z;
e=2*d+x.*y.*z;
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Walter Roberson
Walter Roberson 2015-9-29
The code that Andrei provided does all of them at the same time. No loop is required.
Norzuria Ibrahim
Norzuria Ibrahim 2015-9-29
sorry.my mistake..you already told me how to wrote it above.anyway,thanks guys for your superb answers.

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更多回答（1 个）

WAT
WAT 2015-9-29
编辑：WAT 2015-9-29
It's a little unclear from your question, but if you mean you have 3 dependent variables (x,y,z) each observed at 5 different values of some independent variable (for example, x(t),y(t) and z(t)), and you want the values of c and e at those same times, then all you need to do is
d=x+y+2*z
e=2*d+x.*y.*z
The decimal in front of the multiply tells MATLAB to do the multiplication componentwise, rather than matrix multiplication.
Unless you're required to use a loop (for a HW assignment), in which case it would be something like
d = zeros(1,5);
e = zeros(1,5);
for i = 1:5
d(i) = x(i) + y(i) + 2*z(i);
e(i) = 2*d(i) + x(i)*y(i)*z(i);
end
But you don't want to do it this way unless you're explicitly required to use a loop.
  1 个评论
Norzuria Ibrahim
Norzuria Ibrahim 2015-9-29
编辑：Norzuria Ibrahim 2015-9-29
I think the code you wrote is right. But, the variables x, y and z have values like I wrote above. How to write the data of the variables in matlab and use loop?

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