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Moderator of Mathematica.SE and Celtic goddess.

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Sep
10
comment Relational joining of tables
I think the difference is that this one (I think) assumes unique keys. At least that's what I understand a SQL table id to be.
Sep
8
comment Alternatives to procedural loops and iterating over lists in Mathematica
@d555 - not in this instance. The original poster had used a sequence of definitions, Xarray[some_Integer] rather than a vector with parts. Both approaches are possible in Mathematica.
Sep
5
comment Hodrick–Prescott filter (one-sided version)
@YvesKlett just be aware of some of the pitfalls of this filter. See, for example, Cogley T and JM Nason (1995), ‘Effects of the Hodrick-Prescott Filter on Trend and Difference Stationary Time Series: Implications for Business Cycle Research’, Journal of Economic Dynamics and Control, 19(1–2), pp 253–278.
Sep
4
comment Hodrick–Prescott filter (one-sided version)
@YvesKlett You're welcome - I thought the HP filter was used exclusively in economics?
Aug
28
comment Setting non-standard ImageResolution for EMF export as default
@RolfMertig because it won't be me doing it. It will be end users expecting the process to be at least as straightforward as the process they are currently using. If I can't deliver that, user acceptance could be affected.
Aug
28
comment Why is building a table of function values so much slower than just plotting the function?
You can save about one-third of the time by removing the redundant Evaluate from your Table expression. Also, this result is entirely dependent on the MaxRecursion setting. If you remove this, or leave it in but increase its value, the plot takes longer than the table.
Aug
27
comment How to make MapAt work with Span?
It also works with All, e.g. fakedailydata = Transpose@{DatePlus[{2001, 1}, #] & /@ Range[0, 999], Accumulate[RandomVariate[NormalDistribution[0, 1], {1000}]]}; MapAt[#^2 &, fakedailydata, {All, 2}]. Really handy for time series (date-value pairs).
Aug
19
comment Numbered equations/formulas
hi @earnric, welcome to Mathematica.SE! I have converted your "answer" to a comment because it didn't really address the question.
Aug
19
comment How can I manipulate TemporalData?
@SjoerdC.deVries - indeed, but if you have some actual time series data - say GDP of a country - and you want to do stuff to it like calculate a percentage change or a moving average, the functions below seem quite useful.
Aug
14
comment 3D Phase Portrait with direction fields and sample solution curves
Welcome, amzoti. You can delete your question, but the StackExchange system allows us to mark this question as a duplicate of the other one. This is fine, as people are directed to the right answer, and some Google searches might find this one more easily than the original. So there is no real harm in having duplicates. It is always a good idea to check on the site first to see if your question has already been answered.
Aug
9
comment Defining functions in a loop
Well, that's how I read it, but if the post shoud be reopened, I won't object. I just can't help feeling there is a dupe, but I couldn't find it.
Aug
9
comment Defining functions in a loop
Use Table rather than Do.
Jul
28
comment Simplifying expressions with square roots
@NikolaDimitrov - even members with less rep can format posts. Edits need to be approved if you have less than 2000 rep, but everyone can pitch in.
Jul
28
comment How to make a conditioning plot?
Related: mathematica.stackexchange.com/q/6877/8
Jul
20
comment Importing Excel Spreadsheet containing Array Formulas
Yes, but that's going to be very unpopular with anyone hoping to use Mathematica for visualizing a lot of data stored in Excel. It is clearly a bug in Mathematica.
Jul
19
comment Importing Excel Spreadsheet containing Array Formulas
I wonder if there is a workaround using "Data"?
Jul
8
comment My algorithm produces too many permutations
This is mathematically the same as your previous question. I strongly advise you to avoid using single capital letters as your variables. They can clash with built in definitions. And my previous advice applies. This is a problems where you would be better off rethinking the problem to avoid brute force permutations.
Jul
8
comment Taking averages at certain intervals
I see now what you are trying to do. Have a look at Partition. Mean/@ Partition[data,500] should do what you want for a vector, I think. For a 2D matrix, if what you want is a list of vectors where each vector captures the (non-overlapping) averages of 500-element sublists of each row of the original matrix, then you need: (Mean/@Partition[#,500])/@ data.
Jul
8
comment Taking averages at certain intervals
You are right, redefining your matrix this way is inefficient and can lead to unexpected results. Have a look at MovingAverage in the documentation and see if that does what you need.
Jul
6
comment Unwanted parentheses appearing in a notebook that is opened by a button
Alexei, if this is you, you might want to merge the account you posted this with, with the other account. Please reply to this or flag your post if that's what you want.