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Disagreement of Matrix dimension

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Anandh
Anandh 2011-8-4
Hello Friends,
I have executed the following codes:
X=[8.3 13.9 12.5 22.2 8.3 11.1 18.1 11.1 6.9 6.9 6.9 19.4 9.7 4.2 5.6 12.5 11.1 6.9 8.3 8.3 13.9 9.7 6.9 6.9 8.3 5.6 12.5 4.2 18.1 11.1 4.2 8.3 12.5 15.3 5.6 6.9 13.9 13.9 18.1 12.5 15.3 29.2 36.1 30.6 22.2 40.3 41.7 52.8 50 52.8 61.1 55.6 72.2 69.4 68.1 68.1 76.4 94.4 77.8 101.4 81.9 73.6 93.1 76.4 48.6 52.8 41.7 44.4 43.1 25 26.4 19.4 25 19.4 16.7 13.9 8.3 15.3 5.6 5.6 5.6 5.6 9.7 6.9 2.8 8.3 9.7 8.3 11.1 12.5 15.3 8.3 13.9 4.2 16.7 5.6 8.3 16.7 4.2 11.1 2.8 8.3 5.6 8.3 4.2 11.1 12.5 8.3 8.3 9.7 13.9 15.3 19.4 20.8 25 23.6 25 25 25 33.3 26.4 23.6 27.8 19.4 22.2 19.4 23.6 26.4 15.3 23.6 15.3 26.4 13.9 9.7 15.3 11.1 11.1 18.1 9.7 16.7 18.1 9.7 11.1 22.2 18.1 13.9 19.4 20.8 18.1 13.9 15.3 19.4 13.9 16.7 20.8 12.5 18.1 15.3 15.3 12.5 8.3 12.5 20.8 15.3 15.3 12.5 13.9 9.7 18.1 8.3 19.4 16.7 12.5 12.5 13.9 6.9 9.7 11.1 16.7 5.6 8.3 11.1 4.2 12.5 2.8 12.5 11.1 8.3 9.7 8.3 8.3 18.1 12.5 11.1 8.3 9.7 6.9 12.5 5.6 8.3 0];
M=2;
N = length( X );
Z = ones(N,M) * 1/M; % indicators vector
P = zeros(N,M); % probabilities vector for each sample and each model
t = ones(1,M) * 1/M; % distribution of the gaussian models in the samples
u = linspace(min(X),max(X),M); % mean vector
sig2 = ones(1,M) * var(X) / sqrt(M); % variance vector
C = 1/sqrt(2*pi); % just a constant
Ic = ones(N,1); % - enable a row replication by the * operator
Ir = ones(1,M); % - enable a column replication by the * operator
Q = zeros(N,M);
thresh = 1e-3;
step = N;
last_step = inf;
iter = 0;
min_iter = 10;
when I try to execute the following code,
P = C ./ (Ic*sqrt(sig2)) .* exp( -((X*Ir -Ic*u).^2)./(2*Ic*sig2));
am getting this error:
?? Error using ==> mtimes
Inner matrix dimensions must agree.
The problem I have identified with that code,in particular (X*Ir)is both are matrix but of different sizes, say X = 1R&201C and Ir=1R&1C.
How to handle these different size matrices?
Please help me out.
Also suggest me some alternate codes. Thanks.
kra/-
  2 个评论
Oleg Komarov
Oleg Komarov 2011-8-4
Please format the code with the {} button, will increase the chance of an prompt answer.

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采纳的回答

Andreas Goser
Andreas Goser 2011-8-4
How to debug this:
1. Format the code in a way Oleg asked for. You help others to help you.
2. If you have a matrix dimension error in one line, split the line into sub-operations in oder to see where it fails, e.g.
P = C ./ (Ic*sqrt(sig2)) .* exp( -((X*Ir -Ic*u).^2)./(2*Ic*sig2)); % fails
exp( -((X*Ir -Ic*u).^2)./(2*Ic*sig2)) % fails
-((X*Ir -Ic*u).^2) % fails
X*Ir % fails - there must be at least one cause
3.
>> whos X Ir
Name Size Bytes Class Attributes
Ir 1x2 16 double
X 1x201 1608 double
-> Now it is clear. 1x201 * 1x2 - > That's not going to work. The question still is, what is it that you need to achieve. Just because I could tell you a working operation, I can't tell you what makes sense.
  3 个评论
显示 1更早的评论
Oleg Komarov
Oleg Komarov 2011-8-4
201x1 * 1x2 = 201x2: basics of matrix multiplication, more on wikipedia.
I would suggest to do: (1x2)' * 1x201 = 2x201. Transposing a smaller matrix is more convenient...but it depends also on subsequent operations which at the moment I can't read.
Andreas Goser
Andreas Goser 2011-8-4
I would like to refrain from suggesting a certain operation / implementation.
See the examples in the doc here: http://www.mathworks.com/help/techdoc/ref/arithmeticoperators.html
It lists all the ways to multiply two vectors.

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