how to initialize variables ?

Question

Imene Yed 2021-7-5

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/872428-how-to-initialize-variables

评论： Imene Yed 2021-7-5

Hi I want to initialize my variable calcul_Pression but it doesn't seem to work .

clear all,clc
[t,n]= pfe(); 
if t=0
    calcul_Pression=10^15
end
%Calcul pression:
 calcul_Pression=15000*8.3144621*1e+6*(n(:,1)+n(:,2)+n(:,3)+n(:,4)+n(:,5)...
     +n(:,6)+n(:,7)+n(:,8)+n(:,9)+n(:,10)+n(:,11)+n(:,12)+n(:,13)+n(:,14)...
    +n(:,15)+n(:,16)+n(:,17)+n(:,18)+n(:,19)+n(:,20)+n(:,21)+n(:,22)+n(:,23)+n(:,24)...
     +n(:,25)+n(:,26)+n(:,27)+n(:,28)+n(:,29)+n(:,30)+n(:,31)+n(:,32)+n(:,33)...
     +n(:,34)+n(:,35)+n(:,36)+n(:,37)+n(:,38)+n(:,39)+n(:,40)+n(:,41)...
     +n(:,42)+n(:,43))
 pressure=[t,calcul_Pression]
 plot(t,calcul_Pression,'-r')
 xlabel('Temps')
ylabel('Pression(Pascal)')
legend('pression')
grid minor
grid on

4 个评论
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Walter Roberson 2021-7-5

在 MATLAB Online 中打开

if t=0

That is invalid syntax. Comparison is == not =

Imene Yed 2021-7-5

@Walter Roberson I tried it ,but when I check my workspace at t=0 ,I got other values than 10^15.

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Answer 1

Walter Roberson 2021-7-5

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/872428-how-to-initialize-variables#answer_740508

在 MATLAB Online 中打开

plot(t,calcul_Pression,'-r')

You did not use any marker on that plot() call. That implies that you are expecting t and calcul_pression to both be vectors. But

if t==0

would be equivalent to

if all(t==0)

which would be true only if every single t value is exactly 0. Which is unlikely for a vector of times.

What you just might want is,

%no if before this point!
%straight on after the call to pde():
calcul_Pression=15000*8.3144621*1e+6*(n(:,1)+n(:,2)+n(:,3)+n(:,4)+n(:,5)...
     +n(:,6)+n(:,7)+n(:,8)+n(:,9)+n(:,10)+n(:,11)+n(:,12)+n(:,13)+n(:,14)...
    +n(:,15)+n(:,16)+n(:,17)+n(:,18)+n(:,19)+n(:,20)+n(:,21)+n(:,22)+n(:,23)+n(:,24)...
     +n(:,25)+n(:,26)+n(:,27)+n(:,28)+n(:,29)+n(:,30)+n(:,31)+n(:,32)+n(:,33)...
     +n(:,34)+n(:,35)+n(:,36)+n(:,37)+n(:,38)+n(:,39)+n(:,40)+n(:,41)...
     +n(:,42)+n(:,43));
calcul_Pression(t==0) = calcul_Pression=10^15;