For loop within a function f
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Hello all,
I'm trying to get the following function by using a for loop:
f=@(x) ((0.0011*(x(2:1*N)-x(1:N-1)))'*exp(-0.0078*x(Battery_num*N+1:Battery_num*N+N-1)))*Battery_cost/20 + ((0.0011*(x((N+2):2*N)-x((N+1):(2*N-1))))'*exp(-0.0078*x(Battery_num*N+N-1+1:Battery_num*N+2*(N-1))))*Battery_cost/20+...
((0.0011*(x((2*N+2):(3*N))-x((2*N+1):(3*N-1))))'*exp(-0.0078*x(Battery_num*N+2*(N-1)+1:Battery_num*N+3*(N-1))))*Battery_cost/20 + ((0.0011*(x((3*N+2):(4*N))-x((3*N+1):(4*N-1))))'*exp(-0.0078*x(Battery_num*N+3*(N-1)+1:Battery_num*N+4*(N-1))))*Battery_cost/20;
I have found the pattern with i and j however I don;t know how to get the sum of it, as I get an error because of the x presence.
here is my code:
j=1;
for i=0:Battery_num-1
f=@(x)((0.0011*(x(2+i*N:j*N)-x(2-1+i*N:j*N-1)))' *exp(-0.0078*x(Battery_num*N+1+i*(N-1):Battery_num*N+j*(N-1))))*Battery_cost/20;
j=j+1;
So finally the question is how to add the values for each i. I hope my question is clear
thank you in advance!
5 个评论
Bob Thompson
2018-5-8
If you turn f into an array with indexing then you can sum the values after the for loop is complete.
j=1;
for i=0:Battery_num-1
f(i) = @(x)...
end
summation = sum(f);
Nikolas Spiliopoulos
2018-5-8
Bob Thompson
2018-5-8
Are you actually getting numeric answers out of f? If not, then yes, you would need to use f{i} to produce a cell array.
Also, if you are not getting numeric answers then I don't know how you are going to get a summation. If they are numbers then you should just be able to convert them using cell2num().
Nikolas Spiliopoulos
2018-5-9
dpb
2018-5-9
If you try to create a function array, then you have the same issue as in the original of how to execute it; that syntax is to dereference the particular function out of the array with curlies "{}" followed by the function arguments in parens "()"
回答（2 个）
dpb
2018-5-9
f=@(x)((0.0011*(x(2+i*N:j*N)-x(2-1+i*N:j*N-1)))' *exp(-0.0078*x(Battery_num*N+1+i*(N-1):Battery_num*N+j*(N-1))))*Battery_cost/20;
The above defines the function, it doesn't evaluate it. The function should be written as
fnf=@(x,i,j) ((0.0011*(x(2+i*N:j*N)-x(2-1+i*N:j*N-1)))' *exp(-0.0078*x(Battery_num*N+1+i*(N-1):Battery_num*N+j*(N-1))))*Battery_cost/20;
and then used as
f(i,j)=fnf(x,i,j);
for whatever combinations of i,j it is that you want.
Judicious rewriting to use "dot" operators could probably let you rewrite the function in a vectorized form to eliminate the loop; just should be to get the desired result is indeterminate for lack of complete code from which to try to decipher the intent.
9 个评论
Nikolas Spiliopoulos
2018-5-9
dpb
2018-5-9
Again, the last line defines another anonymous function f instead of evaluating the anon function fnf with the subscripts i,j and the array x passed to it as the definition requires.
The value of Battery_num is embedded in the function from its value at the time the function handle is created; if it is variable then it, too, should be an argument.
As noted before, you haven't told us specifically what it is you're trying to sum over. Also NB: that as you defined the subscript in the anonymous function that x(2+i*N:j*N) that 2+i*N will have to be >= j*N or the subscript index vector will return null and that depending upon what i,j are, you'll get a varying length vector.
I really doubt any of this is what you're really after but you won't tell us that so we can provide a workable solution it seems...
Nikolas Spiliopoulos
2018-5-9
dpb
2018-5-9
I don't care what "function like" you're trying to get, I'm asking what is the end result from first principles you're after; irrespective of the "how" to compute it. I believe your approach is way over-thinking the problem if we knew what the actual problem itself was without the obfuscation of trying to debug non-working code.
Given you have a particular functional form; what are constants in it and what aren't and which of the variables are to be varied over what values to be included in the summation? Knowing that, then we can look at how to code it, but we need the problem definition clearly enunciated first.
Nikolas Spiliopoulos
2018-5-9
编辑：Nikolas Spiliopoulos
2018-5-9
Nikolas Spiliopoulos
2018-5-9
"the function above is for 4 terms (term1+term2+term3+term4). "
Apparently these are the "four terms" that Nikolas Spiliopoulos mentions (I arranged them onto four lines for clarity, and edited them for consistency):
f = @(x)
((0.0011*(x((0*N+2):(1*N))-x((0*N+1):(1*N-1))))'*exp(-0.0078*x(Battery_num*N+0*(N-1)+1:Battery_num*N+1*(N-1))))*Battery_cost/20...+
((0.0011*(x((1*N+2):(2*N))-x((1*N+1):(2*N-1))))'*exp(-0.0078*x(Battery_num*N+1*(N-1)+1:Battery_num*N+2*(N-1))))*Battery_cost/20...+
((0.0011*(x((2*N+2):(3*N))-x((2*N+1):(3*N-1))))'*exp(-0.0078*x(Battery_num*N+2*(N-1)+1:Battery_num*N+3*(N-1))))*Battery_cost/20...+
((0.0011*(x((3*N+2):(4*N))-x((3*N+1):(4*N-1))))'*exp(-0.0078*x(Battery_num*N+3*(N-1)+1:Battery_num*N+4*(N-1))))*Battery_cost/20;
If you are want to define an arbitrary number of "terms" then either vectorize your code or use a loop (implicit or explicit). Certainly adding more and more terms like this would be a poor way to write code, so you are right to ask.
dpb
2018-5-9
I've not tried to compute what the subscripts in terms (x(2:1*N)-x(1:N-1)), x(N+2):2*N)-x((N+1):(2*N-1)) actually turn into numerically (we've no idea what N is here, for starters), but I can't help but believe that storing the array x as either a 2D maybe or even a cell array to simplify the lookup of the proper sequence wouldn't go a long ways towards removing much of the complexity and then be able to write legible (and more importantly working) code.
As is, I still can't fathom what it is your end result is actually supposed to be, sorry...
Nikolas Spiliopoulos
2018-5-9
The answer to your question is already in the title to your question: "For loop within a function f" The attmempts that you showed are the other way around: you define a function inside a loop, but you need a loop inside a function. It is not possible to put a loop inside an anonymous function, so you will need to define a function in a file, e.g. as a nested function:
function out = myfun(x)
out = 0;
for k = 1:Battery_num
out = out + (0.0011*(x(2+(k-1)*N:k*N)-x(2-1+(k-1)*N:k*N-1)))' * ...
exp(-0.0078*x(Battery_num*N+1+(k-1)*(N-1):Battery_num*N+k*(N-1)))) * ...
Battery_cost/20;
end
end
Alternatively it may be possible to vectorize your code, in which case using an anonymous function will still be possible. If you told use the sizes of all of the variables then we might be able to help you with vectorizing the code.
4 个评论
Nikolas Spiliopoulos
2018-5-9
Nikolas Spiliopoulos
2018-5-9
myfun has one input argument x. When you call it from the command line, you will need to supply a value for this argument, e.g.
myfun(1) % or whatever value of |x| you want to use
If you do not supply x then MATLAB has no idea what value to use for the x inside the function. Thus the error.
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