Avoiding for loop and if

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Giovanni Gardan 2020-5-19

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https://ww2.mathworks.cn/matlabcentral/answers/526708-avoiding-for-loop-and-if

关闭： MATLAB Answer Bot 2021-8-20

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I'd like to avoid the following "for loop". Is it possible?

In the following code, the matrix CAR_GEN is the input. This matrix has rows number=1000, and column number=4. In the first column of this matrix there are two possibilities: or 'G' or 'C', and if I have 'C' i have to do the operation under the if-test and finally find the vector ''Scarto''.

Is it possible to check directly if the element of the first column is 'C' and then do the operation in order to find 'Scarto', in order to save time?

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Scarto = zeros (N_nodi_tot - N_nodi_gen,1);                                        %Array initialization
              
                for Riga = 1:100000
                           if  CAR_GEN(Riga,1) == abs('C')
     	                            Ncar = CAR_GEN(Riga,2);
		                    Pcar = CAR_GEN(Riga,3)/Nbase;               
		                    Qcar = CAR_GEN(Riga,4)/Nbase;             
     	                            Nload = Ntot(Riga,1);                   
		                    Scarto(Ncar,1) = Nload - (Pcar + 1i*Qcar);
                            end 
                 end
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Thanks!

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Giovanni Gardan 2020-5-19

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Thank you very much for your answer. Is this the right way to use logical indexing?

Scarto = zeros (N_nodi_tot - N_nodi_gen,1);
cond = (CAR_GEN(:,1) == abs('C'));
                Ncar = CAR_GEN(cond,2);
		Pcar = CAR_GEN(cond,3)/Nbase;              
		Qcar = CAR_GEN(cond,4)/Nbase;                     
     	        Nload = Ntot(cond,1);                       
              
		Scarto(Ncar,1) = Nload - (Pcar + 1i*Qcar);