MATLAB: How is it possible that matlab solves two simultaneous equations which have relation to each other? I am very new with matlab and can not get it done. I want to solve several equations with the euler method bot always get errors.

embedded matlab functioneulermatlab functionnumerical integration

main code :
clear all 
a=0; 
b=10;
N=10; 
y0=0; 
h=(b-a)/N; 
t(1)=a;
R(1)=1;
Pg(1)=1;
P1(1)=1;
c(1)=12;
for n=1:N; 
 t(n+1)=t(n)+h;
 c(n+1)=c(n)+h*g(t(n),c(n));
 Pg(n+1)=1.9*g(t(n),c(n));
 P1(n+1)=8*R(n);
 R(n+1)=R(n)+h*f(t(n),R(n)) ;
end
plot(t,R)
function g:
function g=g(t,c)
g=(45*c)/74;
function f:
function f=f(t,R)
f=(((Pg-P1)*R)/152)-60;
this is the result:
Error :Undefined function or variable 'Pg'
Error in f (line 2)
f=(((Pg-P1)*R)/152)-60
how can I asign the variable Pg and P1 to the equation in the main code

Best Answer

You could just write
Pg = 1;
but a better way, since you know how large the vector will be, is to preallocate the memory:
Pg = ones(1,N+1);
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