Introducing a Variable in simple equation?
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Why is simple code is not working? I am a novice here.
Qc = 40;
Qr = 55;
I = 78;
Qs = 100;
I = sqrt((Qc + Qr -Qs)/R_Ts);
disp(R_Ts)
It is showing Undefined function or variable 'R_Ts'.
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John D'Errico
le 11 Fév 2016
Modifié(e) : John D'Errico
le 11 Fév 2016
You have not defined that variable. How does MATLAB know what it is? You defined all the other variables, but not that one.
If you have the symbolic toolbox, then do this first:
syms R_Ts
Now, it appears as if you want MATLAB to know that you wish to solve for the unknown variable. Computer programs don't read your mind. They do what you tell them to do.
Qc = 40;
Qr = 55;
I = 78;
Qs = 100;
This next line creates an equation of the equality as you posed it, with the unknown variable R_Ts in it.
EQ = I == sqrt((Qc + Qr -Qs)/R_Ts);
And now we apply solve.
R_Ts = solve(EQ,R_Ts)
-5/6084
Or, convert that to a numeric form:
vpa(R_Ts)
ans =
-0.00082182774490466798159105851413544
double(R_Ts)
ans =
-0.000821827744904668
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Mahbubur Rahman
le 11 Fév 2016
Modifié(e) : Walter Roberson
le 11 Fév 2016
Walter Roberson
le 11 Fév 2016
You would still need the
syms R_Ts
before you use R_Ts, and you still need the solve(),
syms R_Ts
Qr = 55;
I = 78;
Qs = 100;
Qc = 45*I - ((R_Ts)^2);
Eq = I == sqrt((Qc + Qr -Qs)/R_Ts)
R_Ts = solve(EQ,R_Ts)
sol =
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