error in subtracting

Question

kash 2012-6-27

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/42138-error-in-subtracting

I have a code
if Sparse_Conc_Index>=1
---------
---------
---------
Class_Image = (Image_Path);
figure,imshow(Class_Image)
else 
    msgbox('Invalid Image ','ALERT')
end
if i do 
F=1-Sparse_Conc_Index
i get
F =  5.1341e-011
please tell how to get  F as zero

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Geoff 2012-6-27

F = 0;

kash 2012-6-27

Hello Geoff i cant understand

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Answer 1

Walter Roberson 2012-6-27

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https://ww2.mathworks.cn/matlabcentral/answers/42138-error-in-subtracting#answer_51918

If F = 1 - Sparse_Conc_Index is positive, then Sparse_Conc_Index >= 1 is false, so your "if" should not be true.

Your problem then reduces down to why Sparse_Conc_Index is not at least 1, which is something we do not know as you do not show how you calculated Sparse_Conc_Index .

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Answer 2

Andreas Goser 2012-6-27

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https://ww2.mathworks.cn/matlabcentral/answers/42138-error-in-subtracting#answer_51895

The point is that 5.1341e-011 IS actually almost zero. It depends now on your application what is the best approach. Very often comparisions are made in a way that you don't compare with ==, but with a tolerance.

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kash 2012-6-27

Andres depending on values of 5.1341e-011 i have to execute for example if this value is greater than 0 i want one operation else other operatiobn for ex

if F>=0

---------

else

-------------

------------

end

here wen i processed my if condition is not working only else part works,please help

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