Make scalar data into a vector

for i=1:length(x)
    a(i)=round(-19.93984628*x(i).^2-19.26822854*x(i)+28.63259561);
    %Use inverse matrix to form system curve equation
    totalX1=sum(X1);
    totalY1=sum(Y1);
    totalA=sum(X1.*Y1);
    totalB=sum(X1.^2);
    totalC=sum(X1.^3);
    totalD=sum(X1.^4);
    totalE=sum(X1.^2.*Y1);
    n=length(X1);
    A1=[n totalX1 totalB;totalX1 totalB totalC;totalB totalC totalD];
    B1=[totalY1;totalA;totalE];
    S1=A1\B1;
    b(i)=round(S1(3)*x(i).^2+S1(2)*x(i)+S1(1));
    if a(i)==b(i)
        fprintf(fid,'\n\nFor Single Pump\n');
        fprintf(fid,'------------------\n');
        fprintf(fid,'The Operating point is at Q=%.3fm3/s\n\n',x(i));
        RQ=0.7; %Requested flow rate 
    end
end

the above is my coding. What I would like to ask for help is: how can I make the 'x' values (scalar) when 'if a(i)==b(i) into a vector? there were multiple output for x values but i want to compile them into a vector.

Hope can help.

Answer 1

[KSSV]

a(i)==b(i) gives a logical output i.e. either 0 or 1. If a and b are vectors a == b, gives a logical vector as output having 1 and satisfied location and 0 at condition not satisfied. To check you can use

any(a==b)

[Walter Roberson]

In other words,

common_values = a(a==b);

[Ting Florence]

I think I am wanna to compile scalar output into one vector, not to check whether they are vector... or i need to check my variable one by one? haha