# create a loop within another loop as the parameter changes

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Alessandro il 6 Feb 2024
Commentato: Alessandro il 10 Feb 2024
hello everyone, i need help. i have an array m*n. for each value of n i need to perform a series of operations where a parameter (Y changes from 0 to 100). the following code needs to be repeated for each value of n.
C=[B,T0]; % matrix
Y=(0:0.1:100); % parameter that must change
Etat=zeros(1001,6681);
for ii=(1:1000);
ws=((1+rhob)/(1+rhob*Y(1,1+ii)))*C(1,1);
wsf=abs(ws);
wr=(((1+rhob)*Y(1,1+ii))/(1+rhob*Y(1,1+ii)))*C(1,1);
wrf=abs(wr);
h=((wsf-C(1,1))*(wrf-C(1,1)))/(C(1,1)*(wsf-wrf));
H=abs(h);
eta=1-(1-eta0)*H;
etar=0.965;
etas=0.97;
Ts= -((C(1,2)*C(1,1))/(0.28*wsf))*(1+(0.64/eta));
Tr=-((C(1,2)*C(1,1))/(wrf*eta))+(wsf/wrf)*((C(1,2)*C(1,1))/(0.28*wsf))*(1+(0.64/eta)));
etat=eta*((Tr*wrf+Ts*wsf)/((Tr*wrf/etar)+(Ts*wsf/etas)));
end
this series of operations must be repeated for all valuesi of the vector column B
thanks
##### 1 CommentoMostra -1 commenti meno recentiNascondi -1 commenti meno recenti
Alessandro il 10 Feb 2024
thank you all i solved it. thank you very much

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### Risposte (2)

Vaibhav il 6 Feb 2024
Modificato: Vaibhav il 6 Feb 2024
Hi Alessandro
I understand that you would like to perform series of operations for each value of "n".
The existing code can be wrapped inside another loop that iterates over the values of "n". Below is a modification of your code to achieve this:
% Define necessary parameters and arrays
% rhob, eta0 etc
% Assuming you have B and T0 defined
% Loop over each value of n
for n = 1:size(C, 2)
C = [B, T0]; % matrix
Y = (0:0.1:100); % parameter that must change
Etat = zeros(1001, 6681);
for ii = 1:1000
ws = ((1 + rhob) / (1 + rhob * Y(1, 1 + ii))) * C(1, n);
wsf = abs(ws);
wr = (((1 + rhob) * Y(1, 1 + ii)) / (1 + rhob * Y(1, 1 + ii))) * C(1, n);
wrf = abs(wr);
h = ((wsf - C(1, n)) * (wrf - C(1, n))) / (C(1, n) * (wsf - wrf));
H = abs(h);
eta = 1 - (1 - eta0) * H;
etar = 0.965;
etas = 0.97;
Ts = -((C(1, 2) * C(1, n)) / (0.28 * wsf)) * (1 + (0.64 / eta));
Tr = -((C(1, 2) * C(1, n)) / (wrf * eta)) + (wsf / wrf) * ((C(1, 2) * C(1, n)) / (0.28 * wsf)) * (1 + (0.64 / eta));
etat = eta * ((Tr * wrf + Ts * wsf) / ((Tr * wrf / etar) + (Ts * wsf / etas)));
end
end
Hope this helps!
##### 2 CommentiMostra NessunoNascondi Nessuno
Alessandro il 6 Feb 2024
thanks for your reply, I omitted that in the calculation of Tr and Ts, I have to consider the values of each row and not just one
Alessandro il 10 Feb 2024
thank you all i solved it. thank you very much

Accedi per commentare.

George Abrahams il 6 Feb 2024
Modificato: George Abrahams il 6 Feb 2024
Unfortunately your code contains mismatched brackets in the calculation of Tr, we don't know the sizes of rhob and eta0, and 2 elements of C are accessed in each loop which appears to contradict the question. For these reasons I can't offer you an exact answer.
It also seems that there's some confusion between columns and rows. Note that in MATLAB the 1st dimension is the row and the 2nd is the column, so A(2,4) references the element in row 2 column 4. The colon operator can be used to select entire rows or columns, for example, A(2,:) references the whole of row 2. I recommend you to read up on Matrix Indexing.
MATLAB is specialized for Array Operations, which I think is probably the answer to your question. With array operations, you can calculate the same equation for every element of the column at once, without needing to loop. For example, C(:,1)*Y(1) multiplies each element in the first column of C by the first element of Y. The alternative would be nested loops, as suggested by @Vaibhav.
##### 3 CommentiMostra 1 commento meno recenteNascondi 1 commento meno recente
George Abrahams il 7 Feb 2024
Yep, there's an unmatched closing parenthesis, see below.
% )
% ( ) ( ) ( ) ( ) ¦
% ( ¦ ¦ ¦ ¦) ( ) ( ¦ ¦ ¦ ¦) ( ) ( ) ¦
% (¦ ¦ ¦ ¦ ¦¦ ¦ ¦) ( ) (¦ ¦ ¦ ¦ ¦¦ ¦ ¦) ( ¦ ¦)¦
% ¦¦ ¦ ¦ ¦ ¦¦ ¦ ¦¦ ¦ ¦ ¦¦ ¦ ¦ ¦ ¦¦ ¦ ¦¦ ¦ ¦ ¦¦¦
Tr=-((C(1,2)*C(1,1))/(wrf*eta))+(wsf/wrf)*((C(1,2)*C(1,1))/(0.28*wsf))*(1+(0.64/eta)));
Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.
Given the following test data, could you please provide some example code to manually calculate all of the values that you want? I think that this would be much clearer and help us to help you.
C = [1 2; 3 4]
C = 2×2
1 2 3 4
Y = [1 2]
Y = 1×2
1 2
Alessandro il 10 Feb 2024
thank you all i solved it. thank you very much

Accedi per commentare.

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