I have a problem writing for loop and if statement

Hi, hope yall are staying safe. I am still learning Matlab. So what I am trying to do is change of Blood Volume ( c ) is equal to change of CSF volume ( f ) if they are not not equal I want to regenerate BV volume and CSF volume until they are equal to each other by using for loop and if statement. Can anyone help me? Thank you so much.

clear
clc
count = 0 ;
N = 10 ;
BV = zeros(N,1) ; %Blood Volume
for i=1:1000                     
    BV_min = 100; %mL/min
    BV_max = 150; %mL/min
    BV_Volume = BV_min - rand(1,1)*(BV_min-BV_max); 
    if BV_Volume < 150 && BV_Volume >100 
          count = count+1 ;
          BV(count) = BV_Volume 
          if count == 10;              
              break
          end
    else
        continue
    end
end
a = BV
b = BV
c = zeros(10,1)
for i = 2:10
    c(i) = b(i-1) - a(i)
end
c = c(2:end)
 
count = 0 ;
N = 10 ;
CSF = zeros(N,1) ; % CSF volume
for i=1:1000                     
    production_rate_min = 0.2; %mL/min
    production_rate_max = 0.6; %mL/min
    production_rate = production_rate_min - rand(1,1)*(production_rate_min- production_rate_max);
    absorption_rate_min = 0.2; %mL/min
    absorption_rate_max = 0.6; %mL/min
    absorption_rate = absorption_rate_min - rand(1,1)*(absorption_rate_min- absorption_rate_max);
    dVdt = production_rate - absorption_rate
    CSF_Volume = (production_rate - absorption_rate)*60*24;  
    if CSF_Volume < 150 && CSF_Volume >100 
          count = count+1 ;
          CSF(count) = CSF_Volume 
          if count == 10;              
              break
          end
    else
        continue
    end
end
 
d = CSF
e = CSF
f = zeros(10,1)
for i = 2:10
    f(i) = e(i-1) - d(i)
end
f = f(2:end)

[Image Analyst]

Possibly, but it would help if you added a lot more comments to your code so we can follow it. The units alone are not enough. And attach plots or something. Make it easy for us to help you. This link is useful. Your code runs, but all I see is a bazillion numbers with no meaning (to me). What do they all mean? Can anything be plotted? There are no errors, so is it working? Otherwise I see you say "want to regenerate BV volume and CSF volume until they are equal to each other by using for loop and if statement." so I'd just do

for k = 1 : length(BV)  % Here's your for loop
    if true % Here's your if statement
        CSF(k) = BV(k); % Here's where they're made equal
    end
end

Help us to understand what's going on without spending 15 minutes trying to figure out what's going on.

By the way, this:

d = CSF
e = CSF
f = zeros(10,1)
for i = 2:10
    f(i) = e(i-1) - d(i)
end
f = f(2:end)

can be done more simply like

f = -diff(CSF);

[Rachel Surridge]

Hello! It looks like there's some randomness involved in both your BV_Volume and CSF_Volume calculation. Are you trying to generate these values until you get them exactly equal by chance?

[Sung Min Kwon]

I am so sorry for the confusion and thank you for the help. First, I was trying to generate 'Blood Volume (BV)' in the range from 100 to 150 randomly. Using same method, I was trying to generate 'Cerebrospinal fluid volume (CSF)' in the range from 100 and 150 randomly. The way I calculated CSF volume is that I first randomly generated production and absorption rate that are between 0.2 and 0.6 and calculated the difference. Then, I calculated CSF volume by multiplying 60 (min) * 24 (hr) to obtain the volume per day. For the outside of for loop, I was trying to find the difference between two consecutive results which are represented by c and f. Basically the whole point of the script above was that I was trying to write (dBV_volume/dt) + (dCSF_volume/dt) = 0. I obtained dBV_volume/dt and dCSF_volume/dt (c and f I guess)but I am not sure how to add for loop and if statement to make them equal to each other. I would like to regenerate c and f values until dBV_Volume/dt and dCSF_Volume/dt untill they are equal to each other. I think I wrote the question wrong in the first place ( I am sorry). I am all ears for the guidance,suggestion and advice. Hope this explanation helped you guys understand little bit of what I was trying. Please let me know if you have other questions. Again, sorry for the confusion and lack of explanation.

[Rachel Surridge]

Thank you for the details!

I understand that c and f are intended to represent discrete values of dCSF_Volume/dt and dBV_Volume/dt between each sample of BV and CSF. If I understand correctly, you want to keep generating c and f until they are equal by chance (since they are based on BV_Volume and CSF_Volume, which are generated with an element of randomness).

You may want a while-loop rather than a for-loop to compare the values of c and f. You can place your entire code in a while loop so that it keeps running until c and f happen to be equal, like so:

flag = true;
while flag
    % insert original code to calculate c and f
    if c==f
        flag = false;
    end
end

If you wanted to generate c once, and keep generating f until it matched c, you could do a similar structure:

% insert original code to calculate BV and c
flag = true;
while flag
    % insert original code to calculate CSF and f
    if c==f
        flag = false;
    end
end

Note: this code compares every element of c to every element of f. c(1) must equal f(1), c(2) must equal f(2), and so on... for the code to terminate.

I'm hesitant to say that this is the answer you're looking for, since the likelihood that f == c is very low, and this while loop may (will almost certainly) run forever. If I've misunderstood your goal, please feel free to correct me!

[Sung Min Kwon]

Wow. Thank you so much!! You are right! It takes forever. Again, thank you so much!! But this is what I wanted though! I think I gotta find a different way to write dCSF_Volume/dt and dBV_Volume/dt between each sample of BV and CSF. Do you have any suggestion? I am all ears! Again, thank you so much!