Would you please tell me what do I have to fix in Binomial distribution code?

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Chris 2022-10-13

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回答： David Hill 2022-10-13

采纳的回答： David Hill

for n = 2:30

for x=1:n;

p(x) = (factorial(n)/(factorial(x)* factorial(n-x)))*((10/230)^x)*(1-(10/230).^(n-x));

end

plot(p)

The graph should come out as one plot that is decreasing, but my graph now has several rising graphs. Would you tell me what do I have to change please?

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Paul 2022-10-13

x should start at 0.

It looks like you're trying to get p for different vaues of n. But each time through the loop overwrites the previous computation of p. So you'll either need to put the plot(0:n,p) command (with a hold) inside the loop, save each p in some sort of data structure and the plot after the loop.

Also, might be interested in this function: nchoosek

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Answer 1

David Hill 2022-10-13

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Note, factorial(30) will not be exact since it has more digits than floating point. The plot is constantly decreasing.

for n = 2:30
    for x=1:n;
        p(x) = (factorial(n)/(factorial(x)* factorial(n-x)))*((10/230)^x)*(1-(10/230).^(n-x)); 
    end
end
diff(p)<0
ans = 1×29 logical array
   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1