if the imaginary part of a complex number is zero

Question

Pooneh Shah Malekpoor 2021-11-9

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1582759-if-the-imaginary-part-of-a-complex-number-is-zero

回答： Gargi Patil 2021-11-12

Hello

Here is my code where I want to see if the imaginary part of a number is zero then int=int+1; however, the imaginary part is not considered as zero though using the command by matlab documentation. what should i do?

int=0
    
    F = @(z)((z-20.6667)^2+((-0.5*(z-10))-14.6667)^2-18.1353^2);
opts = optimoptions('fsolve', 'Display', 'off');
z(1) = fsolve(@(z) F(z), 1+1i, opts);
w(1)=-0.5*(z(1)-10);
z(2)=fsolve(@(z) F(z), 30+1i,opts);
w(2)=-0.5*(z(2)-10);
        for v=1:2
            tt(v)=~any(imag(z(v)));
            if (z(v)>10) && (z(v)<=20 || abs(z(v)-20)<1e-6 )&& tt(v)==1
                if v==2 && abs(z(1)-z(2))<1e-6
                    int;
                else
                    int=int+1;
                   
                    Points(int,:)=[z(v) w(v)];
                     
                end
            end
        end

tt(v) must be 1 for both roots of the equation.

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Answer 1

Gargi Patil 2021-11-12

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在 MATLAB Online 中打开

Hi,

My understanding is that you would like to detect imaginary values equal to zero at the following line:

tt(v)=~any(imag(z(v)));

However, upon closest inspecting the imaginary values of z, they are not exactly zero. For example, the imaginary value of z(1) is 0.000000002392847.

To consider this value as zero, the round function can be used as follows:

nearestDecimalDigit = 4; %set the number of digits as required
tt(v)=~any(round(imag(z(v)), nearestDecimalDigit)); %round to the nearest 4 decimal digits

This sets both the values of tt as 1.