[Graph-support] area bug(?)

[Tom Gettys]

f(x)=dnorm(x,166.3, 26/sqrt(40))



area under path:

from: 173.06

to: 1000

area: 0.05 (correct)



when I add one more zero to the to: value, the area becomes 0.0826, which is
incorrect



Tom Gettys

2929 Warren Street

Eugene, Oregon 97405

[phone]



To dream of the person you would like to be

is to waste the person you are.

[Ivan Johansen]

Post by Tom Gettys
f(x)=dnorm(x,166.3, 26/sqrt(40))
from: 173.06
to: 1000
area: 0.05 (correct)
when I add one more zero to the to: value, the area becomes 0.0826,
which is incorrect

This is an unfortunately side effect of the algorithm (Simpson's
formula) used to calculate the area. When the range gets large rounding
errors starts to accumulate. When I find the time I plan to search for a
better algorithm.

Best regards
Ivan Johansen

[Tom Gettys]

No problem - I thought it might be something like that, but wanted to report
it in case it was a real bug.

Tom Gettys
2929 Warren Street
Eugene, Oregon 97405
[phone]

To dream of the person you would like to be
is to waste the person you are.

-----Original Message-----
From: Ivan Johansen [mailto:***@padowan.dk]
Sent: Monday, May 18, 2009 3:01 PM
To: graph-***@lists.sourceforge.net
Subject: Re: [Graph-support] area bug(?)

Post by Tom Gettys
f(x)=dnorm(x,166.3, 26/sqrt(40))
from: 173.06
to: 1000
area: 0.05 (correct)
when I add one more zero to the to: value, the area becomes 0.0826,
which is incorrect

This is an unfortunately side effect of the algorithm (Simpson's
formula) used to calculate the area. When the range gets large rounding
errors starts to accumulate. When I find the time I plan to search for a
better algorithm.

Best regards
Ivan Johansen


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