How to find maximum value for 3 iterative variables.

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

[Walter Roberson]

Your statement y=a*x+b*k+1; is completely overwriting any previous value of the variable "y", including the use of "y" as an array from the previous iteration of the very next line.

[Shantanu K]

Thanks Walter, can you guide me in finding the maximum value of 'y' & corresponding 'a' & 'b' values

[Walter Roberson]

"y" cannot be simultaneously a scalar and an array. You need to use a different name for one of the two. Or just skip the temporary variable and use

y(p,q,z) = a*x + b*k + 1;

[Shantanu K]

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]

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

[Shantanu K]

Thanks Walter for your help !

Answer 1

[Andrei Bobrov]

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]

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

[Andrei Bobrov]

Oh! Typo, thank you, Walter!

Corrected.

Answer 2

[Walter Roberson]

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]

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]

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"