# Need some help using fminsearch in matlab

• MATLAB
okay so my problem is that I have some data in some arrays z(:,1), u(:,1), s(:,1)

okay I am supposed to use this data with these equations (these are not syntax because I am not sure how to implement this into matlab yet)

H = (omega*(1+z)^3 + (1-omega)*(1+z)^(3*(1+w)))^.5

distLum = (1+z)*integral(1/H,0,z) (that is the integral of 1/H with respect to z from 0 to z)

ufit = 5*log(distLum) + M

basically what I need to do is find the minimum of chi^2

chi^2 = sum of data (u - ufit)^2/s^2)

I hope I explained that sort of. you can see this is quite a problem and not exaclt sure how to use matlab to do this, I was told fminsearch could do the trick. The values I know are z,u,s. My var/para are omega,w,M.

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In general, MATLAB has very good documentation. You can use the Help, or you can type "help fminsearch" (or "help any_function") at the command prompt and it describes the functions. Try this, and then ask some more questions.

I'm going to guess that fminsearch is not the function you want, but I could be wrong... Maybe you can provide more detail about what you're trying to do? Is this some kind of curve fitting method?

-Kerry

I was able to get what I need to, except for one problem.
H is some function. I need to take an integration from 0 to z where z is an array of values and I want to put the answer also into an array to be used

I am trying to take an integration quad(H,0,z), but you cant have that because its not a scalar how can I work around this within function file?

currently I have

function chisquare = chifunc(x,mu_b,z,sig,n)
omega = x(1);
w = x(2);
M = x(3);

H = @(z)hubble(x,z);
distLum = (1+z).* quad(H,0,z); <---error here
mu_fit = 5*log(distLum) + M;
chi = (mu_b-mu_fit).^2./sig.^2;
chisquare = sum(chi);

It sounds like you need a for..loop. It would look something like this:

Code:
integral_array = zeros(size(z));
for i = 1:1:max(size(z)) % Go from 1 to the last element of z, incrementing by 1 every time
end