# How to solve 2 equations with 2 unknown variables and plot the result?

조회 수: 6(최근 30일)
Nabilla Dewi Septiani 2021년 12월 6일
댓글: Nabilla Dewi Septiani 2021년 12월 9일
I have this code to solve 2 equations with 2 unknown variables. And there are 2 known variables that is in a range. It gives the result but only one, where I expect it to be in a range too. Also, I could not plot it.
%Parameters
xin=0.2; xout=0.1; Pr=0.3; qf=1;
x=0:0.1:1;
alpha=0:100:1000;
%For Cross-Flow Module (CF)
y=(1+(x+Pr).*(alpha-1))-((1+(x+Pr).*(alpha-1)).^2-(4.*alpha.*(alpha-1).*x.*Pr)).^0.5/(2.*Pr.*(alpha-1))
y = 1×11
1.0e+03 * -0.0001 0.0398 0.0997 0.1796 0.2795 0.3994 0.5393 0.6992 0.8791 1.0790 1.2989
%qfout-qf=-(1-Pr+((alpha-1).*(x-Pr.*y)))*a
%x-xin=(-(1/qf).*(alpha.*(x-(Pr.*y))*a)+(-x.*ln(qfout/qf))
syms a qfout
E=-(1-Pr+((alpha-1).*(x-Pr.*y)))*a==qfout-qf , (-(1/qf).*alpha.*(x-(Pr.*y))*a)+(-x.*log(qfout/qf))==x-xin;
E =
S=solve(E,a,qfout)
S = struct with fields:
a: 0 qfout: 1
plot(alpha,a)
Error using plot
Data must be numeric, datetime, duration or an array convertible to double.

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### 채택된 답변

KSSV 2021년 12월 6일
You need to convert the sym class to double using double.
plot(double(alpha),double(E))
##### 댓글 수: 1표시숨기기 없음
Nabilla Dewi Septiani 2021년 12월 9일
Thank you sir. I can plot it now
But how to get the value for each array? As I only got one result and it is zero

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R2021b

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