Wolfram Mathematica

12:12 AM

@Szabolcs Not sure if someone already reported back, but it seems the doc-lookup issue is fixed in 11.2.

b3m2a1

12:59 AM

Anyone know what that (List, Bob) is supposed to mean?

It's in all the v11 docs notebooks:

Fold[
 Lookup,
 Options[Import[Documentation`ResolveLink["HeavisideTheta"]],
  TaggingRules],
 {TaggingRules, "Metadata", "titlemodifier"}
 ]

"(List, Bob)"

Seems like it showed up in v8:

FirstCase[
 Import["https://reference.wolfram.com/legacy/v7/ref/HeavisideTheta.\
html",
  {"HTML", "XMLObject"}
  ],
 XMLElement["title", _, {t_}] |
   XMLElement["meta", {___, "title" -> t_, ___}, _] :> t,
 $Failed,
 \[Infinity]
 ]

"HeavisideTheta - Wolfram Mathematica 7 Documentation"

FirstCase[
 Import["https://reference.wolfram.com/legacy/v8/ref/HeavisideTheta.\
html",
  {"HTML", "XMLObject"}
  ],
 XMLElement["title", _, {t_}] |
   XMLElement["meta", {___, "title" -> t_, ___}, _] :> t,
 $Failed,

J. M.

1:27 AM

@Edmund There doesn't seem to be one. Shouldn't be too hard to implement with StringReplace[], tho.

Edmund

@J.M. Yup. I am using StringReplace. Was just wondering as there are probably different illegal characters depending on platform so it would be a nice built-in to have

J. M.

1:46 AM

@Edmund Yes, it's annoying, but maintaining an OS-specific blacklist seems to be the only approach at the moment.

e.g. "?" is OK in *nix, but not in Windows.

Chris K

2:41 AM

Is it just me or are boundary-conditions-at-infinity suddenly popular? ;)

2 hours later…

user21

5:05 AM

@Young, no unfortunately I do not have that. But I am interested in it. If you come up with something I'd be curious to see it. Good luck.

1 hour later…

Anjan Kumar

6:31 AM

Hello guys, a quick question:
How do I extract the coefficients of Cos and Sin from this expression

exp = a0 + (a1 Cos[x] + a2 Sin[x])/a3

I have tried this: exp/. {m0_ + m1_ Cos[_] + m2_ Sin[_] :> {m1, m2}}

I also tried Apart[], but to no avail.

@AnjanKumar Cases[exp, a_ (_Cos | _Sin) :> a, Infinity]

Anjan Kumar

@halirutan Thank you, but it misses out a3 in the denominator.

or if you want to stick with your scheme, you have to get the pattern right

exp /. {_ + (m1_ Cos[_] + m2_ Sin[_])/_ :> {m1, m2}}

ahh, OK. I see what you want.

@AnjanKumar In this case you can use ExpandAll on your expression and then you need to take care of the rational expression.

Anjan Kumar

@halirutan Thank you I got it from the previous answer

This did it
exp /. {_ + (m1_ Cos[_] + m2_ Sin[_])/m3_ :> {m1/m3, m2/m3}}

6:47 AM

Yep, exactly. You just missed the denominator in your first post.

xzczd

7:12 AM

@ChrisK Sorry, I forgot the front page would be overwhelmed, I'll limit the speed of retagging from now on. (Most of the related post has already been tagged though 囧. )

3 hours later…

10:32 AM

I may have made a bit a fool of myself making a big deal out of a simple problem in this question, but for some reason it took me some time to get it. Now I have something else to discuss, but I don't want to make it a question yet, as may be too "opinion based" and potentially yet another silly misunderstanding on my side. Anyhow, here it goes:

I would like to be more thorough in the way I track measurement errors and model uncertainties, and I'm asking myself if assigning suitable Accuracy values to experimental data points would be a sound approach to estimate errors in calculated values.

10:48 AM

Let's say a take a time series data, then SetAccuracy to each point based on the measurement error, rescale with some calibration constant (also an Arbitrary-precision number based on the uncertainty of it) and the Fourier normalize by reference, then Log10. Each point's Accuracy should be properly calculated by Mathematica and a good estimation of the real error of the measurement...

Except by the fact that Mathematica would not consider any Skewness of the error distribution, to first order, would the Accuracy of the result be a good estimation of the real error of the measurement? Or am I missing some internal step on Mathematica's operation that would imply the calculation looses track of the uncertainties?

@rhemans I for one would very welcome a question/discussion about uncertainties in an engineering/measurment context. This is a topic that is in general much neglected by practitioners to the point that even the terminology is most often used wrongly.

@rhemans I really dislike the picture you choose for visualizing precision/accuracy (which I don't blame you for because everybody seems to use this illustration). The reason why I dislike it is that the left hand column illustrates high accuracy/low precision with a higher precision than low accuracy/low precision. This one here is much better: edmundoptics.de/contentassets/087c3fb4b00d4f949128a4a7104938d0/…

11:17 AM

@Sascha Thanks for the better image and your support for a question, I have just change the image. There is already an interesting answer related here in Q27505. But the focus is on keeping High Precision, where I'm more interested on keeping good estimations of the Accuracy of Low Accuracy numbers.

@rhermans I have seen this question (or a similar one in the past) and I still think your question is a good one because it aims at a very different issue. Are you familiar with GUM?

@Sascha "Guide to the Expression of Uncertainty in Measurement"?

yes

@Sascha had to search for it... :)