Can someone help me out with how to structure the answer to this question?

The arrays below contain the price in dollars of three stocks over 10 days.

price_A=[19,18,22,21,25,19,17,21,27,29]

price_B=[22,17,20,19,24,18,16,25,28,27]

Price_C=[17,13,22,23,19,17,20,21,24,28]

Use matlab to determine how many days the price of stock A was above both the price of stock B and the price of stock C.

I'm having trouble structuring the answer to this question. I'm not sure how to do it with all three opposed to just two. I could use a hint a step in the right direction. I was thinking that I need to use find(price_A>..... but after that im not sure what needs to be done.

[Cedric]

In addition to Walter's hint, look at the following

 >> cdt = [3, 8] > [4, 5]
 cdt =
     0     1
 >> class(cdt)
 ans =
     logical

so relational operators (like >) "return" vectors of logicals (true/false symbolized by 1/0), and you can work with such vectors, typically use logical operators on them (e.g &).

[Brian]

I still don't understand, I read the section and there is nothing remotely similar to this question that is being asked. Your hints aren't really helping me.

[Cedric]

What you have to do is to test multiple conditions simultaneously. I'm showing in my comment that the output of the test (using a relational operator) of one condition is a vector of logicals. On the other side, Walter gave you a hint about performing a logical AND between vectors of logicals ..

To illustrate a little more, if you want to test if x is greater than 5 but smaller than 7, you can use nested IF statements

 if x > 5
    if x < 7
      ... do something
    end
 end

which is what you tried to do as you mention in your reply to Walter (and which is a good first approach). Now if x=10 for example, look at what you obtain with the above tests

 >> x = 10 ;
 >> x > 5
 ans =
     1
 >> x < 7
 ans =
     0

both 1 and 0 here are logicals (true, false), as mentioned in my comment, and you can perform logical operations on logicals, so if you wanted to combined the two tests into a single one, hence reducing the nested IF statement to a single IF statement, you could build the following statement

 if (x > 5) & (x < 7)
    .. do something
 end

Play a bit with these concepts and you'll see that they truly apply to your case.

Answer 1

[Walter Roberson]

Hint:

condition1 & condition2

[Brian]

I still don't understand how the conditionals work here. I tried: if (price_B>Price_C) then (price_A>Price_B).

[Image Analyst]

You need to and the conditionals, and then sum them.

price_A > price_B give a logical array for when A cost more than B.

price_A > price_C give a logical array for when A cost more than C.

To find out when A was more than BOTH of them, you need to AND.

A_more_than_both = (price_A > price_B) & (price_A > price_C)

That is an array of 1's and 0's, like 0 0 1 1 0 1 0 0 1 1 0 or whatever. To find out how many days total there are, you need to sum that.

days_above_both = sum(A_more_than_both)

[Walter Roberson]

You could use length(find()) instead of summing them.