summation in matlab with for loop

how can i write the code for the following equation using for loop and summation. here the bold and the underlined part of the equation has to be summed up with change in the i values and the end -i will be the highest constant of n.

W = (kappa*T_in)/(kappa-1)*(((P(i+1)/P(i))^((kappa-1)/kappa))-i);

Answer 1

[Jakob B. Nielsen]

Is it a running sum? In this case something like this, then the i'th entry in runningsum will be the sum of all previous iteration plus the current iteration.

n=100; %lets say you run 100 runs
runningsum=zeros(n,1); 
for i=1:n
    W(i) = (kappa*T_in)/(kappa-1)*(((P(i+1)/P(i))^((kappa-1)/kappa))-i);
    
    runningsum(i)=sum(runningsum)+((P(i+1)/P(i))^((kappa-1)/kappa)); 
end

[vishnuvardhan naidu tanga]

thank you Jakob for your answer, but only the bold part will change with respect to i and i need only the summation of the bold part. everything else remains unchanged. so to be accurate the bold part has to be summed up for n = 100 and the final sum is then included in the whole equation W. so the W is not dependent on i. so is there a way to calculate in such way?

[Jakob B. Nielsen]

Yes - you simply move the evaluation of W to after the loop is completed. (And of course, the running summation in the loop is removed ;) )

n=100; %lets say you run 100 runs
running=zeros(n,1); 
for i=1:n   
    running(i)=((P(i+1)/P(i))^((kappa-1)/kappa)); 
end
W = (kappa*T_in)/(kappa-1)*(sum(running)-n);

[vishnuvardhan naidu tanga]

hello Jakob, Thank you so much it works perfectly fine and i need one other information is there any possibility to write this code as a matlab function in simulink? Please help me if there is any way regarding this.

[Jakob B. Nielsen]

I dont have any simulink experience, but if functions work the same way as they do in 'regular matlab', then you simply do this, save it as RunningSumFunction.m on the path you work in, and call it in your simuling as W=RunningSumFunction(100); to do 100 runs, or 110 to do 110 runs or whatnot.

function W=RunningSumFunction(n)  

running=zeros(n,1); 
for i=1:n   
    running(i)=((P(i+1)/P(i))^((kappa-1)/kappa)); 
end
W = (kappa*T_in)/(kappa-1)*(sum(running)-n);

end

[vishnuvardhan naidu tanga]

Thank you so much for the answer, but thats just a single part of my equation. the whole equation is as follows:

P=zeros(1,n+1 );

P(1) = P_in ;

CR = (P_out/P_in)^(1/n);

for i = 2:n

P(i) = CR*P(i-1 );

P(i+1) = CR*P(i );

end

T=zeros(1,n);

for i = 1:n-1

T(i) = ((P(i+1)/P_in)*(T_in^(kappa/(kappa-1))))^((kappa-1)/kappa);

T(i+1) = ((P(i+1)/P(i))*(T(i)^(kappa/(kappa-1))))^((kappa-1)/kappa);

end

running=zeros(n,1);

for i=1:n

running(i)=((P(i+1)/P(i))^((kappa-1)/kappa));

end

W = (kappa*M)/(kappa-1)*((sum(running))-n);

so this equations i am trying to solve in simulink as a matlab function. i need to define the outputs and the inputs as ports in simulink. so do you have any idea regarding this?