Why do I get this result??

Hello

I have a problem with this code

k=2*A+3*B
if k<3.65
    fr='inf'
elseif 3.65<k<=4.35
    fr='moy'
elseif k>4.35
    fr='sup'
end

why i get this result 'moy'?? it must be 'sup'

k =

      6.4582

fr =

moy

Can you help me to correct this code.

Answer 1

[Evan]

The below line is the culprit:

   elseif 3.65<k<=4.35

Specifying inequalities in matlab isn't done in the same notation as you might when writing them. If you need to find when a value is between an upper and lower bound, do something like this:

    elseif 3.65 <= k && k <= 4.35

The way you have it, matlab evaluates the statement from left to right. So, if k = 6.4582, these will be the steps matlab performs:

1. (3.65 < k) <= 4.35

2. (1) <= 4.35

3. 1

Because the expression in parenthesis is true, it evaluates to "1." This leaves 1 <= 4.35, which will also return 1. But your value was 6.4582, meaning the code didn't do what you intended!

Instead, include each condition in your if statement, separating them with && symbols.

Answer 2

[David Barry]

Try this

k=2*A+3*B
if k<3.65
    fr='inf'
elseif k >= 3.65 && k<= 4.35
    fr='moy'
elseif k>4.35
    fr='sup'
end

[David Barry]

Looks like Evan beat me to it. && is MATLAB command for logical AND.

[David Barry]

Also note that I have changed your code to cope when k = 3.65

[Evan]

Good catch. I didn't notice that. I've updated my post to account for that issue, but credit goes to you. :)

Answer 3

[Sean de Wolski]

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