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How to find maximum value for 3 iterative variables.

Asked by Shantanu K on 7 Mar 2013

In this i have to do following operation mentioned:

Here value of a,b,z are changing continuously. For every value program will calculate value of 'y'.

It will become three dimensional array.

For entire these iterations i have to find out maximum value of 'y' and corresponding value of 'a' & 'b'.

I am facing one more problem, when i formulated array it was showing lot more zeros.

```for p=1:6
a=2*p;
for q=1:6
b=5*q;
```
```            for z=1:100
k=z*z;
x=k*4+1;
y=a*x+b*k+1;
y(p,q,z)=y;```
```            end
end
end```

Shantanu K on 7 Mar 2013
```p=0;
q=0;
z=0;
for p=1:6
for q=1:6
for z=1:100
a=2*p;
b=5*q;
k=z*z;
x=k*4+1;
y(p,q,z)=a*x+b*k+1;
end
end
end
```

How to find maximum value of 'y' and get corresponding value of 'p' and 'q'?

Walter Roberson on 7 Mar 2013

Do you want the 'a' and 'b' (as you wrote the first time) or the 'p' and 'q' (as you write now) ?

Shantanu K on 7 Mar 2013

Thanks Walter for your help !

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Answer by Andrei Bobrov on 7 Mar 2013
Edited by Andrei Bobrov on 7 Mar 2013
```max1 = [-inf 0 0 0];
for p=1:6
for q=1:6
for z=1:100
a=2*p;
b=5*q;
k=z*z;
x=k*4+1;
k1 = a*x+b*k+1;
y(p,q,z) = k1;
if k1 > max1(1), max1 = [k1,p,q,z]; end
end
end
end
```

Walter Roberson on 7 Mar 2013

Re-using the variable "k" could be confusing to me.

Andrei Bobrov on 7 Mar 2013

Oh! Typo, thank you, Walter!

Corrected.

Answer by Walter Roberson on 7 Mar 2013

Before loop:

```maxy = -inf;
a_at_max = -inf;
b_at_max = -inf;
```

then inside the loop, where you assign into y, test to see if the new value is greater than maxy, and if it is, record the a and b values

Shantanu K on 7 Mar 2013

I am not able to understand it sir, can you please elaborate?

then inside the loop, where you assign into y, test to see if the new value is greater than maxy, and if it is, record the a and b values This part i am not able to convert to program.

Walter Roberson on 7 Mar 2013
```if y(p,q,z) > maxy
%then update your record of which "a" and "b" values led to this maximum
end
```

Oh yes and remember to update maxy with the new maximum as well.

Hint: "update" means "do an assignment to"