max and min values in an array

Hello,

I am trying to find positive and negative maximum and minimum in an array.

Lets say I have a Matrix A=[1 -2 5;3 7 -9,4 6 8] if I use max and min functions on A,I get max(A)=[4 7 8] and min(A)=[1 -2 -9]. Since I wanted one singe number I performed max and min operations again.

max(max(A))= 8 and min(min(A))=-9

My requirement here is to get both positive and negative maximum and positive and negative minimum. Is there any way to find that?

Thank you.

[the cyclist]

Your language is not very clear to me. By "maximum" and "minimum", are you talking about the magnitude? So, is the following correct?

• Maximum (magnitude) positive = 8
• Minimum (magnitude) positive = 1
• Maximum (magnitude) negative = -9
• Minimum (magnitude) positive = -2

Answer 1

[the cyclist]

If what I said in my comment is correct, then do the following:

maxMagPos = max(A(A>0))
minMagPos = min(A(A>0))
maxMagNeg = min(A(A<0))
minMagNeg = max(A(A<0))

[Deep P]

Thank you. It works

[the cyclist]

The best form of thanks is upvoting and/or accepting answers. This rewards the contributor, and points future users to good answers.

I suggest you open a new post for your second question, which is quite different in nature, not really related to this one.

[dpb]

@OP If this is something you do more than once, then I'd suggest writing a little utility function that returns the values in a single call; either the four variables or an array depending on how your application most frequently would use the results.

Answer 2

[dpb]

It's the colon operator that's your friend here...

mnx=min(x(:));  % doc colon for details of the "magic" here...