problem with low infinite number

2 Ansichten (letzte 30 Tage)
Trop Trader
Trop Trader am 3 Mär. 2024
Verschoben: John D'Errico am 6 Mär. 2024
Ediff(8,35)
ans =
7.4525e+03
profit(8,35)
ans =
7.4525e+03
bu=minus(profit,Ediff);
bu(8,35)
ans =
1.8190e-12
Why does subtracting 2 equal numbers produce a very small number?

Melden Sie sich an, um diese Frage zu beantworten.

Antworten (2)

the cyclist
the cyclist am 3 Mär. 2024
Bearbeitet: the cyclist am 3 Mär. 2024
Ran in:
Because their floating-point representations are not exactly equal.
You can see that they are not quite equal:
load("matlab_Ediff.mat","Ediff");
load("matlab_profit.mat","profit");
fprintf("Ediff = %16.14f\n",Ediff(8,35))
Ediff = 7452.50000000000182
fprintf("profit = %16.14f",profit(8,35))
profit = 7452.50000000000364
John D'Errico
John D'Errico am 3 Mär. 2024
Ran in:
They only look the same, to 4 decimal places.
format short
x = 1.23456789;
y = 1.23456987;
[x,y]
ans = 1×2
1.2346 1.2346
They certainly look the same to me. But only if I don't look at their actual values, down to the last digits. If I subtract them of course, they are seen to be different.
x - y
ans = -1.9800e-06
Surely you would expect the difference to be non-zero, even though, when displayed as only 5 dignificant digits, they seem identical?
format long
[x,y]
ans = 1×2
1.234567890000000 1.234569870000000

Kategorien

Mehr zu Function Creation finden Sie in Help Center und File Exchange

Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by