Hello!
My code is getting points like 5e-9 and i am putting these points on a vector. However after i run it i get a vector full of zeros.
Is there anyway to keep the real numbers in the vector.
Thank you
MATLAB: Can’t I save very small numbers in a vector
real number
Related Solutions
IEEE double precision floating point cannot represent the number -6e-9 exactly. What you are seeing is the decimal representation of the closest binary floating point bit pattern that IEEE double can represent. This is normal behavior for binary floating point systems. See this link for more discussion:
The "exact" decimal conversion of the binary floating point numbers stored for the numbers in your examples:
>> num2strexact(-1*1e-9)ans = '-1.0000000000000000622815914577798564188970686927859787829220294952392578125e-9'>> num2strexact(-2*1e-9)ans = '-2.000000000000000124563182915559712837794137385571957565844058990478515625e-9'>> num2strexact(-3*1e-9)ans = '-3.0000000000000003936399275115964879745433790958486497402191162109375e-9'>> num2strexact(-4*1e-9)ans = '-4.00000000000000024912636583111942567558827477114391513168811798095703125e-9'>> num2strexact(-5*1e-9)ans = '-5.0000000000000001046128041506423633766331704464391805231571197509765625e-9'>> num2strexact(-6*1e-9)ans = '-6.000000000000000787279855023192975949086758191697299480438232421875e-9'>> num2strexact(-7*1e-9)ans = '-7.00000000000000064276629334271591365013165386699256487190723419189453125e-9'>> num2strexact(-8*1e-9)ans = '-8.0000000000000004982527316622388513511765495422878302633762359619140625e-9'>> num2strexact(-9*1e-9)ans = '-9.0000000000000011809197825347894639236301372875459492206573486328125e-9'Yes if you have badly conditioned (or badly scaled), or practically singular matrix. Usualy you get a warning message when computing the inverse.
This happens with real matrix as well, such as
>> M=magic(6)M = 35 1 6 26 19 24 3 32 7 21 23 25 31 9 2 22 27 20 8 28 33 17 10 15 30 5 34 12 14 16 4 36 29 13 18 11>> iM=inv(M)Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 8.001607e-19. iM = 1.0e+15 * 2.251799813685250 -0.000000000000000 -2.251799813685250 -2.251799813685250 -0.000000000000000 2.251799813685250 2.251799813685250 -0.000000000000000 -2.251799813685250 -2.251799813685250 -0.000000000000000 2.251799813685250 -1.125899906842625 0.000000000000000 1.125899906842625 1.125899906842625 0.000000000000000 -1.125899906842625 -2.251799813685250 0.000000000000000 2.251799813685250 2.251799813685250 0.000000000000000 -2.251799813685250 -2.251799813685250 0.000000000000000 2.251799813685250 2.251799813685250 0.000000000000000 -2.251799813685250 1.125899906842624 0 -1.125899906842624 -1.125899906842624 0 1.125899906842624>> M*iMans = -8.000000000000000 0 8.000000000000000 8.000000000000000 -1.125000000000000 0 0 1.000000000000000 0 0 -0.962843041164940 0.500000000000000 8.000000000000000 -0.000000000000001 -8.000000000000000 -8.000000000000000 -1.773627835340241 8.000000000000000 8.000000000000000 0 -8.000000000000000 -8.000000000000000 0.249352422290674 12.000000000000000 4.000000000000000 0.000000000000000 -4.000000000000000 -4.000000000000000 0.411509381125735 12.000000000000000 8.000000000000000 0 -8.000000000000000 -8.000000000000000 -0.399275413049567 20.000000000000000>> iM*Mans = 0 16 9 -2 4 -2 0 20 9 -2 4 0 4 -2 -2 -1 2 1 2 8 6 0 8 6 0 -4 -9 -2 0 0 0 0 0 0 0 0>> cond(M)ans = 4.700154791029550e+16>>
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