help with for loop

Hello everyone,

I got these two equation. They represent the depth.

The first one is the first depth measured which represents the first value of (Di-1) in the generalized equation below.

I need the code to generate Di until it reaches the condition.

I typed this code buti don't know if it is right as it doesn't fit the calculations i make myself.

Thanks.

% This script represents the Analytical gas lift design

Pks = input('Enter  surface Kick off pressure');
dPkm = input('Enter kick off pressure margin');
Phf = input('Enter Wellhead Pressure');
Gs = input('Enter Static Gradient') ;

Pcs = input('Enter  surface casing pressure');
dPcm = input('Enter casing pressure margin');
Phfd = input('Enter Wellhead desired Pressure');
Gfd = input('Enter desired flowing Gradient') ;

D = (Pks - dPkm - Phf)/(Gs-(Pks - dPkm)/40000);
D=Di;

for Di=1:10

Di = (Pcs - dPcm - Phfd+(Gs-Gfd)*Di)/(Gs-(Pcs - dPcm)/40000);
 
if Di > 5000;
    break
    
end
end

[Walter Roberson]

no you use Di as the for loop variable but you also compute it in the loop . you should use different variables

[Seif Kazamel]

Error in Analytical (line 14)
D = Di;

i changed it to i= 1:10

it gave me the error above

[Walter Roberson]

you have not defined Di at that point

Answer 1

[Daniel Vela]

Hello, please take a look at this code, it might help you fix what you need. Be aware that it might be wise to use a while loop if you want the program to calculate your value more than a determined number of times until it reaches your condition.

userinput1=input('enter value 1');
userinput2=input('enter value 2');
aMinusOne=userinput1+userinput2 %I define my starting value for a(i-1) through formula (use your formula here)
for i=1:10 % The loop will calculate a 10 times and then exit if condition is not.
    a=aMinusOne+5; % the formula takes a(i-1) to calculate the current value of a
    if a>150 %if condition is met, the loop ends and prints some nice message.
       'the condition was reached'
       break
    end
    aMinusOne=a;% we redifine A(i-1) with the most recently calculated value for A for next iteration. 
end