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  • Finding the Formula for a Curve

    - by Mystagogue
    Is there a program that will take "response curve" values from me, and provide a formula that approximates the response curve? It would be cool if such a program would take a numeric "percent correct" (perhaps with a standard deviation) so that it returns simplified formulas when laxity is permissable, and more precise (viz. complex) formulas when the curve needs to be approximated closely. My interest is to play with the response curve values and "laxity" factor, until such a tool spits out a curve-fit formula simple enough that I know it will be high performance during machine computations.

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  • How to make scipy.interpolate give a an extrapolated result beyond the input range?

    - by Salim Fadhley
    I'm trying to port a program which uses a hand-rolled interpolator (developed by a mathematitian colleage) over to use the interpolators provided by scipy. I'd like to use or wrap the scipy interpolator so that it has as close as possible behavior to the old interpolator. A key difference between the two functions is that in our original interpolator - if the input value is above or below the input range, our original interpolator will extrapolate the result. If you try this with the scipy interpolator it raises a ValueError. Consider this program as an example: import numpy as np from scipy import interpolate x = np.arange(0,10) y = np.exp(-x/3.0) f = interpolate.interp1d(x, y) print f(9) print f(11) # Causes ValueError, because it's greater than max(x) Is there a sensible way to make it so that instead of crashing, the final line will simply do a linear extrapolate, continuing the gradients defined by the first and last two pouints to infinity. Note, that in the real software I'm not actually using the exp function - that's here for illustration only!

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  • Evaluating mathematical expressions in Python

    - by vander
    Hi, I want to tokenize a given mathematical expression into a binary tree like this: ((3 + 4 - 1) * 5 + 6 * -7) / 2 '/' / \ + 2 / \ * * / \ / \ - 5 6 -7 / \ + 1 / \ 3 4 Is there any pure Python way to do this? Like passing as a string to Python and then get back as a tree like mentioned above. Thanks.

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  • Logs are filling up with httpclient.wire.content dumps. How can I turn it off?

    - by ?????
    My catalina logs are filling up with gobs of statements like: /logs/catalina.out:2010-05-05 02:57:19,611 [Thread-19] DEBUG httpclient.wire.content - >> "[0x4] [0xc][0xd9][0xf4][0xa2]MA[0xed][0xc2][0x93][0x1b][0x15][0xfe],[0xe]h[0xb0][0x1f][0xff][0xd6][0xfb] [0x8f]O[0xd4][0xc4]0[0xab][0x80][0xe8][0xe4][0xf2][\r]I&[0xaa][0xd2]BQ[0xdb](zq[0xcd]ac[0xa8] on and on forever. I searched every config file in both tomcat and apache for the statements that purportedly turn this on as described here: http://hc.apache.org/httpclient-3.x/logging.html And I don't see where this logging as been enabled. No other .war I deployed does this. The log4j configuration block in the app isn't doing it. Any ideas? I'm using an S3 library for grails that may be the source for these. However when I run this application on my development machine (in both develop and deploy configs), I'm not seeing it.

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  • Express any number as the sum of 4 prime numbers [Doubts]

    - by WarDoGG
    I was give a problem to express any number as sum of 4 prime numbers. Conditions: Not allowed to use any kind of database. Maximum execution time : 3 seconds Numbers only till 100,000 If the splitting is NOT possible, then return -1 What i did : using the sieve of eratosthenes, i calculated all prime numbers till the specified number. looked up a concept called goldbach conjecture which expresses an even number as the summation of 2 primes. However, i am stuck beyond that. Can anyone help me on this one as to what approach u might take ? The sieve of eratosthenes is taking 2 seconds to count primes till 100,000 :(((

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  • Looking for C# framework for plotting scientific data: 2d/3d ...

    - by Ivan
    I need to visualize some scientific calculations. I generally prefer reusing code if there is already a good available instead of inventing wheels each time, that's why I am asking. I need a C# code to draw charts (just outputting a bitmap is ok) of 2d (y=f(x)) and 3d (z=f(x,y)) digital data sets (where any axis can be float, int or datetime), sometimes combined. If I go here and click 3D in the navigation bar on the left, there I can see what I need. But the cheapest version costs $759 there, looks scary for a hobby project of an east-european student :-(

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  • adding up value of array and getting the average

    - by sea_1987
    I have an array that looks similar to this, [4] => Common_Model Object ( [id] => 4 [name] => [date_created] => [last_updated] => [user_id_updated] => [_table] => [_aliases] => Array ( [id] => 4 [name] => [date_created] => [date_updated] => [user_id_updated] => [rating] => 3 [recipe_id] => 5 ) [_nonDBAliases] => Array ( ) [_default] => Array ( ) [_related] => Array ( ) [_enums] => [_alsoDelete] => Array ( ) [_readOnly] => Array ( [0] => date_updated ) [_valArgs] => Array ( ) [_valArgsHash] => Array ( [default] => Array ( ) ) [_valAliases] => Array ( ) [_extraData] => Array ( ) [_inputs] => Array ( ) [_tableName] => jm_ratings [_tablePrefix] => [_niceDateUpdated] => 1st Jan 70 [_niceDateCreated] => 1st Jan 70 [_fetchAdminData] => [_mCache] => [_assets] => Array ( ) ) [3] => Common_Model Object ( [id] => 3 [name] => [date_created] => [last_updated] => [user_id_updated] => [_table] => [_aliases] => Array ( [id] => 3 [name] => [date_created] => [date_updated] => [user_id_updated] => [rating] => 1 [recipe_id] => 5 ) [_nonDBAliases] => Array ( ) [_default] => Array ( ) [_related] => Array ( ) [_enums] => [_alsoDelete] => Array ( ) [_readOnly] => Array ( [0] => date_updated ) [_valArgs] => Array ( ) [_valArgsHash] => Array ( [default] => Array ( ) ) [_valAliases] => Array ( ) [_extraData] => Array ( ) [_inputs] => Array ( ) [_tableName] => jm_ratings [_tablePrefix] => [_niceDateUpdated] => 1st Jan 70 [_niceDateCreated] => 1st Jan 70 [_fetchAdminData] => [_mCache] => [_assets] => Array ( ) ) [2] => Common_Model Object ( [id] => 2 [name] => [date_created] => [last_updated] => [user_id_updated] => [_table] => [_aliases] => Array ( [id] => 2 [name] => [date_created] => [date_updated] => [user_id_updated] => [rating] => 1 [recipe_id] => 5 ) [_nonDBAliases] => Array ( ) [_default] => Array ( ) [_related] => Array ( ) [_enums] => [_alsoDelete] => Array ( ) [_readOnly] => Array ( [0] => date_updated ) [_valArgs] => Array ( ) [_valArgsHash] => Array ( [default] => Array ( ) ) [_valAliases] => Array ( ) [_extraData] => Array ( ) [_inputs] => Array ( ) [_tableName] => jm_ratings [_tablePrefix] => [_niceDateUpdated] => 1st Jan 70 [_niceDateCreated] => 1st Jan 70 [_fetchAdminData] => [_mCache] => [_assets] => Array ( ) ) I wanting to add up the [rating] and get the mean average. But I dont know how do this with PHP, my attempt looks like this, <?php foreach ($rt as $rating) { $total = $rating->rating + $rating->rating } $total / count($rt); ?>

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  • How to compute the dot product?

    - by WizardOfOdds
    I have the following piece of pseudo-C/Java/C# code: int a[]= { 30, 20 }; int b[] = { 40, 50 }; int c[] = {12, 12}; How do I compute the sign of the dot-product AB . AC? I'm only interested in the sign, so I have: boolean signABxAC = ? Now concretely what do I write to get the sign of the dot-product AB . AC?

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  • PHP won't parse MySQL statements

    - by Hussain
    I just installed Apache 2.2.15/PHP 5.3.2/MySQL 5.1.44 on Windows Vista. Apache is working fine, PHP is functional, and MySQL works on the CLI. However, when I try to access MySQL via PHP, I get an error (Fatal error: Call to undefined function mysql_connect()). extension=php_mysql.dll and extension=php_mbstring.dll are uncommented in the php.ini file, and PHP is in the system path. There is no libmysql.dll in either the top level PHP directory or the ext directory. There's a libmySQL.dll file in the MySQL bin directory (which is also in the system path); I tried renaming it, but that doesn't do anything Also, in case anyone wants to know, I originally installed PHP using the MSI installer, but it was missing some DLLs, so I installed from the zip file. I think I've exhausted all my options. Any help on this problem would be very appreciated. Thanks in advance.

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  • Generate RTT values

    - by Jean Gauthier
    Hi all, I'm writing a Java applet where I should be able to simulate a connection between two hosts. Hence I have to generate packet round-trip times at random. These RTTs can go from ~0 to infinity, but are typically oscillating around some average value (i.e. an extremely large or small value is very improbable but possible). I was wondering if anyone had an idea of how I could do this? Thanks in advance

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  • Base 62 conversion in Python

    - by mikl
    How would you convert an integer to base 62 (like hexadecimal, but with these digits: '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'). I have been trying to find a good Python library for it, but they all seems to be occupied with converting strings. The Python base64 module only accepts strings and turns a single digit into four characters. I was looking for something akin to what URL shorteners use.

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  • Python - How to find a correlation between two vectors ?

    - by psihodelia
    Given two vectors X and Y I have to find their correlation, i.e. their linear dependence/independence. Both vectors have equal dimension. A resulted answer should be a floating point number from [-1.0 .. 1.0]. Example: X=[-1, 2, 0] Y=[ 4, 2, -0.3] Find y=cor(X,Y) such that y belongs to [-1.0 .. 1.0]. It should be a simple construction involving a list-comprehension. No external library is allowed. UPDATE: ok, if dot product is enough, then here is my solution: nX = 1/(sum([x*x for x in X]) ** 0.5) nY = 1/(sum([y*y for y in Y]) ** 0.5) cor = sum([(x*nX)*(y*nY) for x,y in zip(X,Y) ]) right?

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  • Calculating rotation in > 360 deg. situations

    - by danglebrush
    I'm trying to work out a problem I'm having with degrees. I have data that is a list of of angles, in standard degree notation -- e.g. 26 deg. Usually when dealing with angles, if an angle exceeds 360 deg then the angle continues around and effectively "resets" -- i.e. the angle "starts again", e.g. 357 deg, 358 deg, 359 deg, 0 deg, 1 deg, etc. What I want to happen is the degree to continue increasing -- i.e. 357 deg, 358 deg, 359 deg, 360 deg, 361 deg, etc. I want to modify my data so that I have this converted data in it. When numbers approach the 0 deg limit, I want them to become negative -- i.e. 3 deg, 2 deg, 1 deg, 0 deg, -1 deg, -2 deg, etc. With multiples of 360 deg (both positive and negative), I want the degrees to continue, e.g. 720 deg, etc. Any suggestions on what approach to take? There is, no doubt, a frustratingly simple way of doing this, but my current solution is kludgey to say the least .... ! My best attempt to date is to look at the percentage difference between angle n and angle n - 1. If this is a large difference -- e.g. 60% -- then this needs to be modified, by adding or subtracting 360 deg to the current value, depending on the previous angle value. That is, if the previous angle is negative, substract 360, and add 360 if the previous angle is positive. Any suggestions on improving this? Any improvements?

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  • Is there any valid reason radians are used as the inputs to trig function in many modern languages?

    - by johnmortal
    Is there any pressing reason trig functions should use radian inputs in modern programming languages? As far as I know radians are typically ugly to deal with except in three cases: (1) You want to compute an arc length and you know the angle of the arc and (2) You need to do symbolic calculus with trig functions (3) certain infinite series expansion look prettier if the input is in radians. None of these scenarios seem like a worthy justification for every programming language I am familiar with using radian inputs for Sin, Cos, Tangent, etc... The third one sounds good because it might mean one gets faster computations using radians (very slightly faster- the cost of one additional floating point multiplication ) , but I am dubious even of that because most commonly the developer had to take an extra step to put the angle in radians in the first place. The other two are ridiculous justifications for all the added obscurity.

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  • Trying to install mod_proxy in Apache-Httpd-2.2.15

    - by Dspace
    Hello, I have spent the afternoon trying to install the mod_proxy module into apache. I have tried ./configure --prefix=/opt/apache2 --enable-proxy --enable-proxy-http ./configure --prefix=/opt/apache2 --enable-module=proxy After it finishes installing, navigating to /opt/apache2/modules only shows one file: httpd.exp. It seems that the module is not being installed. Any help is appreciated. Thanks.

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  • Need some help understanding this problem

    - by Legend
    I was wondering if someone could help me understand this problem. I prepared a small diagram because it is much easier to explain it visually. Problem I am trying to solve: 1. Constructing the dependency graph Given the connectivity of the graph and a metric that determines how well a node depends on the other, order the dependencies. For instance, I could put in a few rules saying that node 3 depends on node 4 node 2 depends on node 3 node 3 depends on node 5 But because the final rule is not "valuable" (again based on the same metric), I will not add the rule to my system. 2. Execute the request order Once I built a dependency graph, execute the list in an order that maximizes the final connectivity. First and foremost, I am wondering if I constructed the problem correctly and if I should be aware of any corner cases. Secondly, is there a closely related algorithm that I can look at? Currently, I am thinking of something like Feedback Arc Set or the Secretary Problem but I am a little confused at the moment. Any suggestions? PS: I am a little confused about the problem myself so please don't flame on me for that. If any clarifications are needed, I will try to update the question.

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  • How do I find the largest factor of an integer in mysql

    - by Bill H
    I am trying to write a select query that will dynamically determine the minimum number of items that can be packaged together. I am having trouble with one part of the query. ... CASE WHEN (pid.product_id) THEN 1 WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 11 = 0)) THEN CEILING(p.inner_pack / 11) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 7 = 0)) THEN CEILING(p.inner_pack / 7) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 6 = 0)) THEN CEILING(p.inner_pack / 6) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 5 = 0)) THEN CEILING(p.inner_pack / 5) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 4 = 0)) THEN CEILING(p.inner_pack / 4) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 3 = 0)) THEN CEILING(p.inner_pack / 3) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 2 = 0)) THEN CEILING(p.inner_pack / 2) ELSE p.inner_pack END AS min_pack ... What I want to do is find the largest factorial of an integer (p.inner_pack) that is under 12. Is there a better way to do this in mysql?

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  • Simple encryption - Sum of Hashes in C

    - by Dogbert
    I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

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  • Apache as Reverse Proxy for CouchDB

    - by Overflown
    I'm thinking of a web app that uses CouchDB extensively, to the point where there would be great gains from serving with the native erlang HTTP API as much as possible. Can you configure Apache as a reverse proxy to allow outside GETs to be proxied directly to CouchDB, whereas PUT/POST are sent to the application internal logic (for sanitation, authentication...)? Or is this unwise -- the CouchDB built-in authentication options just seem a little weak for a Web App. Thanks

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  • OPTICS Clustering algorithm. How to get the best epsilon

    - by Marco Galassi
    I am implementing a project which needs to cluster geographical points. OPTICS algorithm seems to be a very nice solution. It needs just 2 parameters as input(MinPts and Epsilon), which are, respectively, the minimum number of points needed to consider them as a cluster, and the distance value used to compare if two points are in can be placed in same cluster. My problem is that, due to the extreme variety of the points, I can't set a fixed epsilon. Just look at the image below. The same points structure but in a different scale would result very different. Suppose to set MinPts=2 and epsilon = 1Km. On the left, the algorithm would create 2 clusters(red and blue), but on the right it would create one single cluster containing all of the points(red), but I would like to obtain 2 clusters even on the right. So my question is: is there any kind of way to calculate dynamically the epsilon value to get this result? Thank you very much and excuse my for my poor english. Marco

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  • Ruby BigDecimal sanity check (floating point newb)

    - by Andy
    Hello, Hoping to get some feedback from someone more experienced here. I haven't dealt with the dreaded floating-point calculation before... Is my understanding correct that with Ruby BigDecimal types (even with varying precision and scale lengths) should calculate accurately or should I anticipate floating point shenanigans? All my values within a Rails application are BigDecimal type and I'm seeing some errors (they do have different decimal lengths), hoping it's just my methods and not my object types... Thanks!

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