How to use the loops in this situation?

Hello!3[1 1+randperm(9)];

I have two conditions with every number comming after first digit i.e x(1). let say

a= 10*rand(1,10); 
b =10*rand(1,10) ; 
c = 10*rand(1,10); 
d = 10*rand(1,10)

# for all values of i

if (a(i)<b(i+1) && c(i)<d(i+1))

# create new x until the above condition satisfied

otherwise proceed with the x

x = [1 1+randperm(9)];
for i = 2: nodes
   while( (a(i)<b(i+1) && c(i)<d(i+1)))
     goto(x)
       return
   end
end

Answer 1

[Elijah Smith]

So, there are a few things that I noticed right off the bat.

1. I have not seen the syntax "while if ..." and I don't believe that is correct.
2. you used the return keyword but your code is not a function (to my knowlage)
3. you have nothing but "goto(x)" in your while loop thus if the condition is true it will interate forever
4. As another person metioned b, c and d are "0" because 0 times anything is still 0 : (b =0*rand(1,10); c = 0*rand(1,10); d = 0*rand(1,10)) (not a copy and paste error) this means that you will never execute the while loop.
5. there is not a "goto" function in matlab. if this is a custom function please add the code for it.
6. once you get to the last interation of the for loop (if I understand what your doing) you will get "index exceeds array bounds" error because some arrays are indexed with "i+1"

But if I understand what you are doing (which this is a long shot) here is some code that may help:

x = [1 1+randperm(9)];
a= 10*rand(1,10); b = rand(1,10); c = rand(1,10); d = rand(1,10);
for i = 2:length(x)
    if ((a(i)<b(i+1)) && (c(i)<d(i+1)))
        goto(x(i))
    end
end

I may be able to answer better if you:

1. Upload the goto function code
2. better explain what the goal of the code is (what are you using it for)
3. explain the need for the while loop
4. explain what you were trying to do with the return keyword

[Elijah Smith]

Also, yes I know that my code has errors but that is because of things that I mentioned like "exceeds array bounds." I can fix these errors I just don't know the goal of the code so I don't know how to best fix them.

[Elijah Smith]

So, after a bit of research, I found that there is a goto function in simulink and I have not done anything with simulink so if that is what your question is about I can't help you. sorry.

[Muhammad Usama]

t was 10* rand not 0* rand for b c and d.

I am doing a vehicle routing problem and generating a random route x for a vehicle.

Initially, I have some goods in the vehicle. The vehicle will visit all the nodes and will collect goods from some nodes and drop goods at other nodes.

I just want to model the condition that vehicle should not vist the node of the node demand is greater than the goods in the vehicles or not visit if goods to be picked are more than the capacity of the vehicle .

Moreover, I just have written goto function just to highlight my requirement. I have used the function you said but that is not working in this case I dont know why .

[Muhammad Usama]

it was not while if it was jist while I have made correction

[Elijah Smith]

are the nodes the elements of x and the value the demand?

[Elijah Smith]

please also explain what a b c and d are so I can understand the while loop.

[Walter Roberson]

Where did you get that (non-MATLAB) code that you are trying to understand? The one that includes the goto(x) ? It looks more like pseudo-code.

[Elijah Smith]

this is wrong im sure but if you comment like this Ill be able to help you better:

%Create nodes with node demands
x = [1 1+randperm(9)];
%create 4 random arrays
a= 10*rand(1,10); b = 10*rand(1,10); c = 10*rand(1,10); d = 10*rand(1,10);
%for every node after the first
for i = 2:length(x)
    %check the condition that compares random arrays
    if ((a(i)<b(i+1)) && (c(i)<d(i+1)))
        %if true exicute a function for the current node
        goto(x(i))
    end
end

[Elijah Smith]

Walter, if you are asking me, I got it from his question. As I stated, from my knowlage, goto is not in matlab. I was asking if it was a custom function.

[Muhammad Usama]

yes it is just pseudo-code.

[Muhammad Usama]

"a" is the availbe goods in the Truck while visiting node "i", "b" is the goods demand at any node "i" ( or the quantity of goods to be unloaded at node "i"). c is the availbe space in the vehicle to load goods from any node 'i" , and "d" is the quantity to be picked up from the "i:" node.

[Elijah Smith]

Okay, maybe this is more of what you meant:

x = [1 1+randperm(9)];
a= 10*randi([1 10], 1, 10); %goods in the truck at the arrival to each node
b = 10*randi([1 10], 1, 10); %demand at each node
c = 10*randi([1 10], 1, 10); %availible space at arrival each node
d = 10*randi([1 10], 1, 10); %amount of goods to be picked up
%for every node
for i = 1:length(x)
    %check to see if you have enough packages and have enough space for packages:
    %if the truck has enough goods (a(i)>b(i)) and enough space (c(i)>d(i))
    if a(i)>b(i) && c(i)>d(i)
        %if true then do stuff
    else
        fprintf("the truck made it to node %d", i);
        break;
    end
end

The only other issue I see is that this is not very realistic simply because the truck would not have a random amount of space or goods at each node it would change as goods were dropped off and recieved. You would want to add something inside of the if statement to change the values for goods and space in the truck on each interation (as if the truck was actually losing and gaining packages).

If this is not what you were asking then I may still not understande your question.

[Elijah Smith]

using these random numbers you will only move to a new node about 1/4 of the time and it will be near imposible to make it to node 10.

[Muhammad Usama]

Before this loop I have calculated lated quantity of goods for every random path

[Elijah Smith]

yes, but since they are determined randomly you have a specific chance as to continuing in the path. A real life situation would require you to set a, b, c and d manually and then let them update each other as nodes are visited.

Does the code I provided help? if not please Clarify what you are Asking. Your original post does not contain a question. You used loops already so it is hard to answer the question of "how to use loops in the situation?"

[Muhammad Usama]

thank you

yes, you are right values of a,b,c and d are fixed not random. my question is just to run the loop untill i get the feasible pattern.