# how to initialize variables ?

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Imene Yed on 5 Jul 2021
Commented: Imene Yed on 5 Jul 2021
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
Imene Yed on 5 Jul 2021
@Walter Roberson I tried it ,but when I check my workspace at t=0 ,I got other values than 10^15.

Walter Roberson on 5 Jul 2021
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 on 5 Jul 2021
thank you so much you've helping me a lot .

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