How to create multidimensional arrays of distribution objects?

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Alex
Alex 2013-10-2
评论： Alex 2013-10-3
Hi I am just working on a larger program that works with two random distributed Variables:
X for incoming products(Production) Y for outgoing products(Demand)
both random variables have 2 parameters, so a and b belong to X and c and d belong to Y. I am now working on a combination of both and need a combined distribution stored in a 4 dimensional array to reflect all possible combinations. My initial guess to create an "empty" array of the matching dimensions was just:
a=[1 2 3 4];
b=[5 6];
c=[7 8 9];
d=[1 2 3 4 5];
for i=1:length(a)
for j=1:length(b)
for k=1:length(c)
for l=1:length(d)
test(i,j,k,l)=makedist('normal',0,0);
end
end
end
end
the problem is now that matlab seems to have no default distribution-object included in the libraries and following error occurs:
During array expansion: No default is defined for class 'prob.NormalDistribution'. Method 'getDefaultScalarElement' in superclass prob.ProbabilityDistribution is missing or incorrectly defined.
I was lucky find a solution for 2 dimensions that just sets the elements before a default element is needed and i expanded this to a 3 dimensional array. However, if i try to expand the solution in the same way to 4 dimensions the error occurs again:
clc
clear
a=[100 5 5 7];
b=[10 4 4 5 6];
c=[100 2 6 7 9 9];
d=[1 4 5 5];
for i=1:length(a)
test(i,:)=makedist('normal',0,0);
for j=1:length(b)
test (i,j)=makedist('normal',0,0);
end
end
test
for i=1:length(a)
test2(i,:,:)=makedist('normal',0,0);
for j=1:length(b)
test2 (i,j,:)=makedist('normal',0,0);
for k=1:length(c)
test2 (i,j,k)=makedist('normal',0,0);
end
end
end
test2
for i=1:length(a)
test2(i,:,:,:)=makedist('normal',0,0);
for j=1:length(b)
test2 (i,j,:,:)=makedist('normal',0,0);
for k=1:length(c)
test2 (i,j,k,:)=makedist('normal',0,0);
for l=1:length(d)
test2(i,j,k,l)=makedist('normal',0,0);
end
end
end
end
test3
While the first two versions are running perfectly, even as intended and give the matching distribution-object arrays, but the 4 dimensional one gives following error:
During array expansion:
No default is defined for class 'prob.NormalDistribution'.
Method 'getDefaultScalarElement' in superclass prob.ProbabilityDistribution is missing or incorrectly defined.
Error in Untitled (line 29)
test3(i,:,:,:)=makedist('normal',0,0);
When i define the 3 dimensional array first, set test3=test2, the error shifts to the line
test3(i,j,k,l)=makedist('normal',0,0);
as soon as d=[ ] has more than one element. i also tried to set the d loop around the other 3 loops but the error always occurs when the pointer of the fourth dimension shifts to 2. I dont know why this error occurs only with 4 dimensions, to my understanding it should also occur with 3 dimensions, or both versions should run propperly, i cant see why one works and the other one not.
It would be very kind if somebody could help me with this problem or give me a hint how to create this AxBxCxD array of distribution objects in another way. Thank you for your help
  2 个评论
Matt J
Matt J 2013-10-2
编辑：Matt J 2013-10-2
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采纳的回答

Tom Lane
Tom Lane 2013-10-2
This looks like something that we should fix in a future release. Meanwhile, perhaps you would find this work-around useful:
a = makedist('normal'); % create a single distribution object
a = repmat(a,[2 3 4 5]); % expand it to the desired size
a(2,3,4,5) = makedist('Weibull'); % fill in the values you really want

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