how to initialize variables ?

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

[Image Analyst]

What is the value of t (so we know if line 4 got executed)? Regardless, line 7 should get executed and assign something to calcul_Pression.

To fix, see this link:

Debugging in MATLAB | Doug's MATLAB Video Tutorials

[Imene Yed]

I verified my variables on my workspace .at t=0 I found another value not 1e15 ,it didn't execute the line 4

[Walter Roberson]

if t=0

That is invalid syntax. Comparison is == not =

[Imene Yed]

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

Answer 1

[Walter Roberson]

 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;

This calculates calcul_Pression at all locations, and then overwrites the calculated value at any location corresponding where t matches 0.

[Imene Yed]

thank you so much you've helping me a lot .