Grid points inside a domain MATLAB IF statement evaluates TRUE when it shouldn't

Asked Dec 09 '15 at 19:48

Active Dec 09 '15 at 20:30

Viewed 20 times

I have this function that is supposed to, taking into consideration, certain constraints construct a grid. My question is why even though I have an if conditional that is supposed to be false it evaluates true. I have commented the part with the values. Any ideas why this is happening?

The function is:

function b = inside(x,y)

    rightwall = @(y) y+0.16;
    leftwall = @(y) y+0.1;

    b = false;
    if y < 0.04 && y > 0 
        if x < rightwall(y)
            b = true;
        end
    elseif y >= 0.04  && y <0.06
        if x > leftwall(y) && x < rightwall(y)
            lw = leftwall(y)     % lw = 0.1400 is equal to x and if statement   
                                 % should not run
            rw = rightwall(y)    % lw = 0.2000
            x = x                % lw = 0.1400 
            b = true;
        end
    elseif y >= 0.06 && y <= 0.20 
        if x > 0.16 && x < 0.20
            b = true;
        end
    end
end

edited Dec 09 '15 at 20:30

asked Dec 09 '15 at 19:48

Lebowski

Are you sure `x` and `lw` are equal? Or are they just two numbers both close to `1.4`? – aschepler Dec 09 '15 at 20:20
@ aschepler I am sure I have used format long – Lebowski Dec 09 '15 at 20:23
You should never compare floats for equality. Incorporate a tolerance. – sco1 Dec 09 '15 at 20:28
@ excaza how would one do that? – Lebowski Dec 09 '15 at 20:30
Subtract one from the other and see if it's less than a threshold. – sco1 Dec 09 '15 at 20:35
You can `round` your values to two digits, it should work then. Apart from that its a problem discussed a billion times. Therefore closed with the canonical answer. – Robert Seifert Dec 09 '15 at 21:20
@ excaza and @ thewaywewalk It works now. Good idea with the tolerance! Thank you for your help! :) – Lebowski Dec 10 '15 at 07:33

Grid points inside a domain MATLAB IF statement evaluates TRUE when it shouldn't

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