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

[Geoff]

F = 0;

[kash]

Hello Geoff i cant understand

Answer 1

[Walter Roberson]

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 .

Answer 2

[Andreas Goser]

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.

[kash]

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