For loop to do 900 subtractions

Question

Terry Poole 2022-3-1

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1661175-for-loop-to-do-900-subtractions

评论： David Hill 2022-3-1

So I have a Double Difference equation in the form of y = (sqrt(BR^2 - B1^2) - sqrt(BB^2 - B1^2)) - (sqrt(BR^2 - B2^2) - sqrt(BB^2 - B2^2)).......

and so on with B(i) being 901 numbers so (n1 - n2 - n3 - n4 - n5 ....... - n901)

How would I even begin to write a loop to do this so I don't have to cut and paste 901 times?

Please be patient with me my brain is so far gone, i've been at this code for about 100 hours now.

B = [X_mat_base, Y_mat_base, Z_mat_base];
BB = [xyz(1), xyz(2), xyz(3)];
BR = zeros(1, 3);
B = [X_mat_base, Y_mat_base, Z_mat_base];
for i = 1:length(BB(:, 1)) 
    yx(i) = (sqrt(BR(1)^2 - B(i, 1).^2) - sqrt(BB(1)^2 - B(i, 1).^2));
end

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Answer 1

Walter Roberson 2022-3-1

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https://ww2.mathworks.cn/matlabcentral/answers/1661175-for-loop-to-do-900-subtractions#answer_907240

在 MATLAB Online 中打开

y = sqrt((BR - B).^2 + (BB - B).^2);

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Walter Roberson 2022-3-1

"and so on with B(i) being 901 numbers so (n1 - n2 - n3 - n4 - n5 ....... - n901)"

That implied to me that you have a single variable named B and that where you wrote B2 in your code you meant B(2) .

If you have individual variables B1, B2, B3, ... B901 then... don't .

http://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

David Hill 2022-3-1

Your signs are making no sense to me. Your question had all minus signs after the first term. I am confused as to what you want. You should be able to excute without a for-loop. Above some of your BB terms are plus and some are minus

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