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Is there a c# lib to fit data to normal distribution?

I found a similar question but it has no exact answer.
What I need is given a real world data set: List<double> and assume it fits a normal distribution. I need to get the distribution(the mean and sdv). I am using math.net to calculate data in my application. Can math.net do this and how? Or is there any other C# library can do this?
Thanks a lot.

Wikipedia gives you formulas to calculate the estimates of the normal distribution parameters. The expressions are simple so you actually don't need any third party libraries to perform the calculations.

I'm on the CenterSpace NMath team. We use a robust trust region minimizer to solve this nonlinear fitting problem. Depending on your data you may be able to do this with the more widely accessible Levenberg-Marquardt minimization algorithm well documented on wikipedia.
http://www.centerspace.net/distribution-fitting-demo/
No our library isn't free...but this code may give you some ideas.
Best,
Paul

block TEA in c#

Using block tea (XXTEA), how can I convert encrypted text into human readable form?
string encryptedText = "ASDFSDAFSADFSDFSDFSDAF"; (assume it is in correct format)
I have the key/pwd also.

There is a Visual Basic implementation of the block tea algorithm here:
http://www.blog-dotnet.com/post/Tiny-Encryption-Algorithm-(TEA)-in-Visual-BasicNET.aspx
Block tea is meant to be easily implementable, so you shouldn't have a hard time converting that to C# (or compiling it into a .NET assembly with VB and then referencing it from .NET).
You should use the above as a base and then modify it as per the XXTEA algorithm, found here:
http://en.wikipedia.org/wiki/XXTEA
Again, it's meant as being easy to implement, so you shouldn't be too hard. If there are specific parts you are having issues with, please make sure to follow up.

Edit1: Core XTEA algorithm in C# with other parts in VB.NET at CodeProject
Tiny Encryption Algorithm and XTEA for the Compact Framework at CodeProject
Here is a JavaScript Implementation of the XXTEA algorithm and here.
Here is a Pascal implementation of all of them.
With all the other answers you should be able to put an implementation together. Once you do it, make a blog or report back here so it is recorded for the next guy!

I found this https://github.com/WooCode/xxTea which is a C# implementation, with unit tests provided. I haven't verified it's accuracy.

Lex/Yacc for C#?

Actually, maybe not full-blown Lex/Yacc. I'm implementing a command-interpreter front-end to administer a webapp. I'm looking for something that'll take a grammar definition and turn it into a parser that directly invokes methods on my object. Similar to how ASP.NET MVC can figure out which controller method to invoke, and how to pony up the arguments.
So, if the user types "create foo" at my command-prompt, it should transparently call a method:
private void Create(string id) { /* ... */ }
Oh, and if it could generate help text from (e.g.) attributes on those controller methods, that'd be awesome, too.

I've done a couple of small projects with GPLEX/GPPG, which are pretty straightforward reimplementations of LEX/YACC in C#. I've not used any of the other tools above, so I can't really compare them, but these worked fine.
GPPG can be found here and GPLEX here.
That being said, I agree, a full LEX/YACC solution probably is overkill for your problem. I would suggest generating a set of bindings using IronPython: it interfaces easily with .NET code, non-programmers seem to find the basic syntax fairly usable, and it gives you a lot of flexibility/power if you choose to use it.

I'm not sure Lex/Yacc will be of any help. You'll just need a basic tokenizer and an interpreter which are faster to write by hand. If you're still into parsing route see Irony.
As a sidenote: have you considered PowerShell and its commandlets?

Also look at Antlr, which has C# support.

Still early CTP so can't be used in production apps but you may be interested in Oslo/MGrammar:
http://msdn.microsoft.com/en-us/oslo/

Jison is getting a lot of traction recently. It is a Bison port to javascript. Because of it's extremely simple nature, I've ported the jison parsing/lexing template to php, and now to C#. It is still very new, but if you get a chance, take a look at it here: https://github.com/robertleeplummerjr/jison/tree/master/ports/csharp/Jison

If you don't fear alpha software and want an alternative to Lex / Yacc for creating your own languages, you might look into Oslo. I would recommend you to sit through session recordings of sessions TL27 and TL31 from last years PDC. TL31 directly addresses the creation of Domain Specific Languages using Oslo.

Coco/R is a compiler generator with a .NET implementation. You could try that out, but I'm not sure if getting such a library to work would be faster than writing your own tokenizer.
http://www.ssw.uni-linz.ac.at/Research/Projects/Coco/

I would suggest csflex - C# port of flex - most famous unix scanner generator.

I believe that lex/yacc are in one of the SDKs already (i.e. RTM). Either Windows or .NET Framework SDK.

Gardens Point Parser Generator here provides Yacc/Bison functionality for C#. It can be donwloaded here. A usefull example using GPPG is provided here

As Anton said, PowerShell is probably the way to go. If you do want a lex/ yacc implementation then Malcolm Crowe has a good set.
Edit: Direct Link to the Compiler Tools

Just for the record, implementation of lexer and LALR parser in C# for C#:
http://code.google.com/p/naive-language-tools/
It should be similar in use to Lex/Yacc, however those tools (NLT) are not generators! Thus, forget about speed.

Constructing a simple interpreter

I’m starting a project where I need to implement a light-weight interpreter.
The interpreter is used to execute simple scientific algorithms.
The programming language that this interpreter will use should be simple, since it is targeting non- software developers (for example, mathematicians.)
The interpreter should support basic programming languages features:
Real numbers, variables, multi-dimensional arrays
Binary (+, -, *, /, %) and Boolean (==, !=, <, >, <=, >=) operations
Loops (for, while), Conditional expressions (if)
Functions
MathWorks MatLab is a good example of where I’m heading, just much simpler.
The interpreter will be used as an environment to demonstrate algorithms; simple algorithms such as finding the average of a dataset/array, or slightly more complicated algorithms such as Gaussian elimination or RSA.
Best/Most practical resource I found on the subject is Ron Ayoub’s entry on Code Project (Parsing Algebraic Expressions Using the Interpreter Pattern) - a perfect example of a minified version of my problem.
The Purple Dragon Book seems to be too much, anything more practical?
The interpreter will be implemented as a .NET library, using C#. However, resources for any platform are welcome, since the design-architecture part of this problem is the most challenging.
Any practical resources?
(please avoid “this is not trivial” or “why re-invent the wheel” responses)

I would write it in ANTLR. Write the grammar, let ANTLR generate a C# parser. You can ANTLR ask for a parse tree, and possibly the interpreter can already operate on the parse tree. Perhaps you'll have to convert the parse tree to some more abstract internal representation (although ANTLR already allows to leave out irrelevant punctuation when generating the tree).

It might sound odd, but Game Scripting Mastery is a great resource for learning about parsing, compiling and interpreting code.
You should really check it out:
http://www.amazon.com/Scripting-Mastery-Premier-Press-Development/dp/1931841578

One way to do it is to examine the source code for an existing interpreter. I've written a javascript interpreter in the D programming language, you can download the source code from http://ftp.digitalmars.com/dmdscript.zip
Walter Bright, Digital Mars

I'd recommend leveraging the DLR to do this, as this is exactly what it is designed for.
Create Your Own Language ontop of the DLR

Lua was designed as an extensible interpreter for use by non-programmers. (The first users were Brazilian petroleum geologists although the user base has broadened considerably since then.) You can take Lua and easily add your scientific algorithms, visualizations, what have you. It's superbly well engineered and you can get on with the task at hand.
Of course, if what you really want is the fun of building your own, then the other advice is reasonable.

Have you considered using IronPython? It's easy to use from .NET and it seems to meet all your requirements. I understand that python is fairly popular for scientific programming, so it's possible your users will already be familiar with it.

The Silk library has just been published to GitHub. It seems to do most of what you are asking. It is very easy to use. Just register the functions you want to make available to the script, compile the script to bytecode and execute it.

The programming language that this interpreter will use should be simple, since it is targeting non- software developers.
I'm going to chime in on this part of your question. A simple language is not what you really want to hand to non-software developers. Stripped down languages require more effort by the programmer. What you really want id a well designed and well implemented Domain Specific Language (DSL).
In this sense I will second what Norman Ramsey recommends with Lua. It has an excellent reputation as a base for high quality DSLs. A well documented and useful DSL takes time and effort, but will save everyone time in the long run when domain experts can be brought up to speed quickly and require minimal support.

I am surprised no one has mentioned xtext yet. It is available as Eclipse plugin and IntelliJ plugin. It provides not just the parser like ANTLR but the whole pipeline (including parser, linker, typechecker, compiler) needed for a DSL. You can check it's source code on Github for understanding how, an interpreter/compiler works.

Big integers in C#

Currently I am borrowing java.math.BigInteger from the J# libraries as described here. Having never used a library for working with large integers before, this seems slow, on the order of 10 times slower, even for ulong length numbers. Does anyone have any better (preferably free) libraries, or is this level of performance normal?

As of .NET 4.0 you can use the System.Numerics.BigInteger class. See documentation here: http://msdn.microsoft.com/en-us/library/system.numerics.biginteger(v=vs.110).aspx
Another alternative is the IntX class.
IntX is an arbitrary precision
integers library written in pure C#
2.0 with fast - O(N * log N) - multiplication/division algorithms
implementation. It provides all the
basic operations on integers like
addition, multiplication, comparing,
bitwise shifting etc.

F# also ships with one. You can get it at Microsoft.FSharp.Math.

The System.Numerics.BigInteger class in .NET 4.0 is based on Microsoft.SolverFoundation.Common.BigInteger from Microsoft Research.
The Solver Foundation's BigInteger class looks very performant. I am not sure about which license it is released under, but you can get it here (download and install Solver Foundation and find the Microsoft.Solver.Foundation.dll).

I reckon you could optimize the implementation if you perform all the operations on BigInts that are going to return results smaller than a native type (Eg. int64) on the native types and only deal with the big array if you are going to overflow.
edit
This implementation on codeproject, seems only 7 times slower ... But with the above optimization you could get it to perform almost identically to native types for small numbers.

Here are several implementations of BigInteger in C#.
I've used Mono's BigInteger implementation, works pretty fast (I've used it in CompactFramework)
Bouncy Castle
Mono

I'm not sure about the performance, but IronPython also has a BigInteger class. It is in the Microsoft.Scripting.Math namespace.

Yes, it will be slow, and 10x difference is about what I'd expect. BigInt uses an array to represent an arbitrary length, and all the operations have to be done manually (as opposed to most math which can be done directly with the CPU)
I don't even know if hand-coding it in assembly will give you much of a performance gain over 10x, that's pretty damn close. I'd look for other ways to optimize it--sometimes depending on your math problem there are little tricks you can do to make it quicker.

I used Biginteger at a previous job. I don't know what kind of performance needs you have. I did not use it in a performance-intensive situation, but never had any problems with it.

This may sound like a strange suggestion, but have you tested the decimal type to see how fast it works?
The decimal range is ±1.0 × 10^−28 to ±7.9 × 10^28, so it may still not be large enough, but it is larger than a ulong.
There was supposed to be a BigInteger class in .NET 3.5, but it got cut.

This won't help you, but there was supposed to be a BigInteger class in .Net 3.5; it got cut, but from statements made at PDC, it will be in .Net 4.0. They apparently have spent a lot of time optimizing it, so the performance should be much better than what you're getting now.
Further, this question is essentially a duplicate of How can I represent a very large integer in .NET?

See the answers in this thread. You will need to use one of the third-party big integer libraries/classes available or wait for C# 4.0 which will include a native BigInteger datatype.

This Looks very promising. It is a C# Wrapper over GMP.
http://web.rememberingemil.org/Projects/GnuMpDotNet/GnuMpDotNet.html
There are also other BigInteger options for .Net here in particular, Mpir.Net

You can also use the Math.Gmp.Native Nuget package that I wrote. Its source code is available on GitHub, and documentation is available here. It exposes to .NET all of the functionality of the GMP library which is known as a highly-optimized arbitrary-precision arithmetic library.
Arbitrary-precision integer are represented by the mpz_t type. Operations on these integers all begin with the mpz_ prefix. For examples, mpz_add or mpz_cmp. Source code examples are given for each operation.