I tried to generate a sequence with a specific interval, but the output skips some intervals.

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Fortia Alfeche 2023-1-22

0
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https://ww2.mathworks.cn/matlabcentral/answers/1898350-i-tried-to-generate-a-sequence-with-a-specific-interval-but-the-output-skips-some-intervals

评论： Stephen23 2023-1-22

采纳的回答： DGM

mat = [];

interval = -0.10;

max = 1.00;

i = 0;

for a=1.00:interval:0.00

for b=1.00:interval:0.00

for c=1.00:interval:0.00

if a+b+c == max

mat(i+1,:) = [a,b,c];

i=i+1;

end

mat

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Fortia Alfeche 2023-1-22

This is suppose to generate 66 combinations, but i'm getting less

Stephen23 2023-1-22

在 MATLAB Online 中打开

Note that you can easily get rid of the loops:

mxv = 1;
[X,Y,Z] = ndgrid(0:0.1:1);
M = [X(:),Y(:),Z(:)];
M(abs(sum(M,2)-mxv)>1e-9,:) = []
M = 66×3
    1.0000         0         0
    0.9000    0.1000         0
    0.8000    0.2000         0
    0.7000    0.3000         0
    0.6000    0.4000         0
    0.5000    0.5000         0
    0.4000    0.6000         0
    0.3000    0.7000         0
    0.2000    0.8000         0
    0.1000    0.9000         0

And there are your 66 triples :)

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Answer 1

DGM 2023-1-22

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1898350-i-tried-to-generate-a-sequence-with-a-specific-interval-but-the-output-skips-some-intervals#answer_1153675

编辑：DGM 2023-1-22

在 MATLAB Online 中打开

I missed the comparison.

You're dealing with floating-point numbers. You can expect exact equality tests to fail due to rounding errors. This comment contains a number of links to related threads on the topic. Other people have explained it better than I can.

https://www.mathworks.com/matlabcentral/answers/1771170-infinite-loop-when-decimals-are-added#comment_2292205

You can test for equality within some tolerance

mat = [];
interval = -0.10;
maxval = 1.00;
i = 0;
for a=1.00:interval:0.00
    for b=1.00:interval:0.00
        for c=1.00:interval:0.00
            thissum = a+b+c;
            if abs(thissum-maxval) < 1E-14
                mat(i+1,:) = [a,b,c];
                i=i+1;
            end
        end
    end
end
mat
mat = 66×3
    1.0000         0         0
    0.9000    0.1000         0
    0.9000         0    0.1000
    0.8000    0.2000         0
    0.8000    0.1000    0.1000
    0.8000         0    0.2000
    0.7000    0.3000         0
    0.7000    0.2000    0.1000
    0.7000    0.1000    0.2000
    0.7000         0    0.3000