how to express a formula for modelFun fo nlinfit

Hello, guys,

I have the formula (convolution):

where

and C is a matrix 1x40 and t is also a matrix of 1x40.

I want to use the first formula for non-linear least square fit (nlinfit), but I don't know how to write modelFun to express this formula, where MTT is a parameter, which I need to estimate.

Thanks for a reply!

Donatas

Answer 1

[Star Strider]

I made several guesses as to what you are doing, but this seems to work:

% Create data:
t = linspace(0, 1, 40);
C = t;
% y = conv(t,exp(-t),'same');
y = conv(exp(-t/7),t);

% Objective function for curve fit
% w = @(P,t) conv(C, exp(-t/P),'same');
w = @(P,t) conv(C, exp(-t/P));

xv = 0:length(y)-1;

B = nlinfit(t, y, w, 1)
yp = w(B,t);

figure(1)
plot(xv, y, 'xb')
hold on
plot(xv, w(B,t), '-r')
hold off
grid

Note that there are 'full', 'same' and 'valid' options with the conv function. Use the one that most closely suits your needs.