Filter löschen
Filter löschen

Help to understand a strange behaviour

2 Ansichten (letzte 30 Tage)
Ivan
Ivan am 1 Apr. 2012
WTF is the following: (noticed ocationally)
>> clear
>> sind(30)
ans =
-0.8660
>> whos
Name Size Bytes Class Attributes
ans 1x1 8 double
after restart:
>> sind(30)
ans = 0.5000
(R2010b)
  5 Kommentare
Geoff
Geoff am 1 Apr. 2012
What do you get when you plot?
x = -720:720; plot(x, sind(x));
Ivan
Ivan am 2 Apr. 2012
plot looks like normal, but drops to -1 at -720:
>> sind(-720)
ans =
-1

Melden Sie sich an, um zu kommentieren.

Akzeptierte Antwort

Jan
Jan am 2 Apr. 2012
I asked Google for "Matlab bug sind" and found:
My conclusion: Ask MathWorks for a bugfix of your version. It is easy to insert a workaround as M-file in your toolbox folder:
function Y = sind(X)
Y = sin(X * 0.017453292519943295769236954843959);

Weitere Antworten (2)

Jan
Jan am 1 Apr. 2012
Does
which sind -all
reveal any unexpected details?
  2 Kommentare
Ivan
Ivan am 2 Apr. 2012
no. i think this is normal:
>> sind(30)
ans =
-0.8660
>> which sind -all
built-in (C:\MATLAB\toolbox\matlab\elfun\@double\sind) % double method
built-in (C:\MATLAB\toolbox\matlab\elfun\@single\sind) % single method
C:\MATLAB\toolbox\distcomp\parallel\@codistributed\sind.m % codistributed method
Ivan
Ivan am 2 Apr. 2012
The two contiguous commands give:
>> sind(30)
ans =
0.500000000000000
>> sind(30)
ans =
-0.866025403784439

Melden Sie sich an, um zu kommentieren.


Ivan
Ivan am 2 Apr. 2012
Thank you, Jan. Yes, i'm now using sin with argument in radians and that's ok. But this issue made me suspicious about all my results ever got with MatLab... Its very sad (
  1 Kommentar
Jan
Jan am 2 Apr. 2012
I agree that such bugs reduce the confidence. Therefore it would be great great great, if MathWorks offers a similar service as most other programs: Automatic download of patchs and bugfixes. Even a dynamically created list of known bugs would be helpful, while the bugs list at http://www.mathworks.com/support/bugreports/ is still too hidden for standard users. In addition it is weak: I do not find a report when I'm searching for "sind" on "all releases". Is it possible that this bug has not been reported?
It seems like this bug is either not reproducible or there is no or a not sufficiently powerful unittest for the elementary functions.
Please contact the technical support. The more votes they get the better for the users and the company.

Melden Sie sich an, um zu kommentieren.

Community Treasure Hunt

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

Start Hunting!

Translated by