Why is my while loop not working?

Question

Leo Tu 2021-7-7

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https://ww2.mathworks.cn/matlabcentral/answers/874178-why-is-my-while-loop-not-working

评论： KSSV 2021-7-14

From this code, I am looking to get the nll values for all s = 0:999 where s is a parameter. When I run it, it runs very slow and only gives out one value of nll. Can anyone help me with getting the nll values for all values of the parameter s from 0 to 999.

% Initial parameter values
s = 0;
mu = 0.1;
om = 0.01;
% AT is a row vector
while s<=999
    for t = s+1:length(AT)
        k = abs(s:-1:(s-t+1));
        id = [(t-1):-1:0]+1;
        lambda(t) = mu+sum(om.^k.*AT(id))/sum(om.^k);
        j = 1:length(lambda);
        nll = -sum(j.*log(lambda(j)))+sum(lambda(j));  
    end
    s = s+1;
end

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DGM 2021-7-8

编辑：DGM 2021-7-8

在 MATLAB Online 中打开

Is nll supposed to be a 2D rectangular array, or is it supposed to be a triangular array or a vector? Obviously, the code as given simply generates a scalar output, but this:

t = s+1:length(AT)

implies that the output is a triangular matrix of some shape, since the number of inner loop cycles varies with each pass of the outer loop.

For clarification:

a = 1:10
a = 1×10
     1     2     3     4     5     6     7     8     9    10
b = 3+1:10
b = 1×7
     4     5     6     7     8     9    10
c = 3+(1:10)
c = 1×10
     4     5     6     7     8     9    10    11    12    13

It doesn't make sense that the output should be a vector either, since nothing in the inner loop appears to depend prior passes. It would just be discarding calculated data.

EDIT:

Here's this. I have no idea if this even makes sense, but it makes numbers. I doubt it's right, but I have no idea what it's supposed to do.

AT = 1:10;
% Initial parameter values
mu = 0.1;
om = 0.01;
srange = [0 9];
s = srange(1):srange(2);
nll = zeros(numel(AT),numel(s));
for si = 1:numel(s)
    t = s(si)+1:numel(AT);
    for ti = 1:numel(t)
        k = abs(s(si):-1:(s(si)-t(ti)+1));
        id = ((t(ti)-1):-1:0)+1;
        lambda(t(ti)) = mu+sum(om.^k.*AT(id))/sum(om.^k);
        % this changes size only for the first pass, which seems wrong 
        % this means col1 values of nll are skewed wrt other columns
        j = 1:length(lambda);
        % store all the results
        nll(ti,si) = -sum(j.*log(lambda(j)))+sum(lambda(j));
    end
end
nll
nll = 10×10
    1.0047  -46.7848  -45.2013  -41.5583  -36.0918  -29.0874  -20.8972  -11.9727   -2.9242    5.3554
    1.6204  -46.6161  -44.6436  -40.6113  -34.7554  -27.3616  -18.7821   -9.4682   -0.0303         0
    1.3258  -46.4974  -44.2457  -39.9338  -33.7983  -26.1250  -17.2658   -7.6723         0         0
   -0.2183  -46.4059  -43.9363  -39.4060  -33.0523  -25.1607  -16.0833         0         0         0
   -3.2647  -46.3315  -43.6830  -38.9736  -32.4409  -24.3702         0         0         0         0
   -8.0146  -46.2687  -43.4685  -38.6073  -31.9228         0         0         0         0         0
  -14.6354  -46.2144  -43.2826  -38.2897         0         0         0         0         0         0
  -23.2704  -46.1665  -43.1185         0         0         0         0         0         0         0
  -34.0450  -46.1238         0         0         0         0         0         0         0         0
  -47.0705         0         0         0         0         0         0         0         0         0

David Hill 2021-7-13

Better describe the equation of lambda with respect to s and your constants.

KSSV 2021-7-14

One reason for slow is you have not initiated lambda.

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Why is my while loop not working?

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Why is my while loop not working?

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