# Matlab code running loops to meet conditions

## Homework Statement

This is not homework but I am trying to solve a problem to see to general a set of numbers for the grassmanian equations to use in something else.[/B]

I have five variables a,b,c,d,e. a-b,a-c,a-d,a-e,b-a,b-c,.....etc so that none of them are the same so it generates all numbers from 1,2,3,4,....20 in modular 21. Clearly a,b,c,d,e can not be the same since it will obviously not generate all the numbers. Below is my matlab code.

a,b,c,d,e must be in the {0,1,2,3,....20}

The code does not even output anything.

## The Attempt at a Solution

Matlab:
clear all;
close all;
k=21;
flag =0;
for i =0:16
a=i;
if flag ==1
break;
end
for j=1:17
b=j;
if flag == 1
break;
end
for h =2:18
c= h;
if flag == 1
break;
end
for l=3:19
d=l;
if flag ==1
break;
end
for p=4:20
e=p;

g1=a-b;
g2=a-c;
g3=a-d;
g4=a-e;
g5=b-a;
g6=b-c;
g7=b-d;
g8=b-e;
g9=c-a;
g10=c-b;
g11=c-d;
g12=c-e;
g13=d-a;
g14=d-b;
g15=d-c;
g16=d-e;
g17=e-a;
g18=e-b;
g19=e-c;
g20=e-d;
G=[ mod(g1,k), mod(g2,k), mod(g3,k), mod(g4,k), mod(g5,k), mod(g6,k), mod(g7,k), mod(g8,k), mod(g9,k), mod(g10,k), mod(g11,k), mod(g12,k), mod(g13,k), mod(g14,k), mod(g15,k), mod(g16,k), mod(g17,k), mod(g18,k), mod(g19,k), mod(g20,k)];
S=sort(G);
AllElements=[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20];
true=isequal(S,AllElements);
if (true == 1)
flag = 1;
break;
end
end
end
end
end
end

Last edited:

jedishrfu
Mentor

However it would be better if you can fix the indenting too.

donpacino
Gold Member
what is the code supposed to output?

Oh yeah I forgot to code that. It is suppose to just stop when the condition is met that the entire G = {1,2,3,4,5,....20} is generated from the values of a,b,c,d,e and I just want the values of a,b,c,d,e.

donpacino
Gold Member
the values of abcd & e are stored in your answers variable....
just print it....
or add a line below that says

I tried that, but when I run the code my workspace is empty.

donpacino
Gold Member
that is true. So there is one way to clear your workstation, whcih is to use the clear all command
you have code after it, there the code must not run.

If I were you I would check my while loop, or remove it all together, infinite loops are no fun

I removed the while loop, which I do not think is actually necessary. It does have a workspace, but the code is breaking at an incorrect solution of
S =

1 1 1 1 2 2 2 3 3 4 17 18 18 19 19 19 20 20 20 20. When it should be S = 1 2 3 ....20.

I resolved my issue. Thanks!