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  • Conditional Counting in Mathematica

    - by 500
    Considering the following list : dalist = {{1, a, 1}, {2, s, 0}, {1, d, 0}, {2, f, 0}, {1, g, 1}} I would like to count the number of times a certain value in the first column takes a certain value in column 3. So in this example my desired output would be: {{1,1,2}, {1,0,1}, {2,1,0}, {2,0,2}} Where the latest sublist {2,0,2} being read as: When the value is 2 in the first column, a corresponding value (same row in matrices world) in column 3 of 0 is present twice. I hope this is not to confusing. I added the second Column to convey the fact that the columns are distant to each other. If possible, no reordering should happen. EDIT : {1,2,3,4,5} {1,0} are the exact values taken by the columns I am actually dealing with in my data. I know I am missing the correct description. Please edit if you can and know it. Thank you

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  • Two quick Mathematica questions

    - by sciguy
    How do I remove the numbers on the x-axis only not the y-axis? Is it possible to shift the y-axis without shifting the functions? What I mean is, instead of having the y-axis at x = 0, could I have it at x = -5?

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  • How do I get Mathematica to thread a 2-variable function over two lists, using functional programmin

    - by Leah Wrenn Berman
    Lets say I have a function f[x_, y_], and two lists l1, l2. I'd like to evaluate f[x,y] where x runs over the list l1 and y runs over the list l2, and I'd like to do it without having to make all pairs of the form {l1[[i]],l2[[j]]}. (Motivation: I'm trying to implement some basic Haskell programs in Mathematica. In particular, I'd like to be able to code the Haskell program isMatroid::[[Int]]->Bool isMatroid b =and[or[sort(union(xs\\[x])[y]'elem'b|y<-ys]|xs<-b,ys<-b, xs<-x] I think I can do the rest of it, if I can figure out the original question, but I'd like the code to be Haskell-like. Any suggestions for implementing Haskell-like code in Mathematica would be appreciated.)

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  • Why is process not being displayed by TOP

    - by drN
    I am running a Mathematica script (this question probably doesn't fit in Mathematica.SE however) and I know that it generally takes up a lot of RAM and loads up my cores. However, althought pgrep MathKernel is showing a pid, I find that top doesn't show this in the top processes, although I notice that it is taking up about 2.25GB of the 8GB available to me. pmap -x my_process_id total kB 2243132 1907404 1892108 AND ps aux | grep MathKernel dnaneet 20837 12.6 23.3 2234944 1907404 pts/1 Sl 09:23 8:01 /share/apps/mathematica/8.0.4/SystemFiles/Kernel/Binaries/Linux-x86-64/MathKernel -runfirst $TopDirectory="/share/apps/mathematica/8.0.4" -script ./dcm_10micrometer_2x -- ./dcm_10micrometer_2x ps aux shows that the process is taking about 12% (In asterisks) dnaneet 20601 0.0 0.0 68264 1660 pts/1 Ss 09:15 0:00 -bash **dnaneet 20837 12.2 23.3 2234944 1907404 pts/1 Sl 09:23 8:01 /share/apps/mat** dnaneet 21922 0.0 0.0 65604 948 pts/1 R+ 10:29 0:00 ps -aux Did this process fail and is the MathKernel just lingering?

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  • Mathematica Plot3D does not produce a plot when graphing a user-defined function?

    - by pythonscript
    I'm writing a simple Mathematica implementation of the black-scholes model and using Plot3D to plot the pricing surface. However, when I run this code, no plot is produced. My call and put functions to produce correct values when run separately, but no plot is produced. Code: Clear[d1, d2, call, put, stockPrice, strikePrice, riskFreeRate, timeToExp, volatility] d1[stockPrice_, strikePrice_, riskFreeRate_, timeToExp_, volatility_] := (Log[stockPrice / strikePrice] + (riskFreeRate + 0.5*volatility^2)*timeToExp) / (volatility * Sqrt[timeToExp]) d2[stockPrice_, strikePrice_, riskFreeRate_, timeToExp_, volatility_] := d1[stockPrice, strikePrice, riskFreeRate, timeToExp, volatility] - volatility*Sqrt[timeToExp] call[stockPrice_, strikePrice_, riskFreeRate_, timeToExp_, volatility_] := stockPrice * CDF[NormalDistribution[0, 1], d1[stockPrice, strikePrice, riskFreeRate, timeToExp, volatility]] - strikePrice * Exp[-riskFreeRate*timeToExp] *CDF[NormalDistribution[0, 1], d2[stockPrice, strikePrice, riskFreeRate, timeToExp, volatility]] Plot3D[call[stockPrice, 500, 0.0030, timeToExp, 0.39], {stockPrice, 10, 1000}, {timetoExp, 0.0833333, 5}] Other plots, like this sample from the reference, do work. Plot3D[{x^2 + y^2, -x^2 - y^2}, {x, -2, 2}, {y, -2, 2}, RegionFunction -> Function[{x, y, z}, x^2 + y^2 <= 4], BoxRatios -> Automatic]

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  • Mathematica quickie: About making cells Input cells by default.

    - by andrz
    I'm going through some lecture notes, Fundamentals of Mathematica Programming (see the .nb file there). I'd like to be able to do the exercises right there in the notebook; but for some reason I can't figure out how to make the default cell an Input cell. In other words, when I'm clicking in that notebook to create a new cell--in the exercises--the cell is by default a text cell. I'd like for it to be an Input cell so that I don't have to manually change it each time. Ideas?

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  • Mathematica: get number of arguments passed to a function?

    - by dbjohn
    How do I get the number of arguments passed to a function, such as Plus[2,3,4,5] has 4 arguments passed to it. I was thinking it may involve the use of the function Length and getting the arguments into a list. The intention is to iterate an operation based on the number of arguments for a function. There is probably a simple solution or function but I haven't come across it yet. Any other ways or suggestions are welcome as well?

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  • How do I maximize a function in Mathematica which takes in a variable length list as input?

    - by Mike
    I have a time-series like function which gives an output based on a list of real numbers(i.e. you can run the function on a list of 1,2,3,... real numbers). The issue I'm encountering is how to maximize the function for a given list length(subject to a set of constraints). I could fix the function to a fixed number of real numbers(i.e. f [x_Real, y_Real] instead of f[x_List]) and treat x and y as the first two elements of the list, and call Maximize on the function, but this is not really elegant. I want to be able to easily change the number of elements in the list. What is the best way to optimize a function like I described, which takes a list as an argument, for a fixed list length?

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  • How to solve generic algebra using solver/library programmatically? Matlab, Mathematica, Wolfram etc?

    - by DevDevDev
    I'm trying to build an algebra trainer for students. I want to construct a representative problem, define constraints and relationships on the parameters, and then generate a bunch of Latex formatted problems from the representation. As an example: A specific question might be: If y < 0 and (x+3)(y-5) = 0, what is x? Answer (x = -3) I would like to encode this as a Latex formatted problem like. If $y<0$ and $(x+constant_1)(y+constant_2)=0$ what is the value of x? Answer = -constant_1 And plug into my problem solver constant_1 > 0, constant_1 < 60, constant_1 = INTEGER constant_2 < 0, constant_2 > -60, constant_2 = INTEGER Then it will randomly construct me pairs of (constant_1, constant_2) that I can feed into my Latex generator. Obviously this is an extremely simple example with no real "solving" but hopefully it gets the point across. Things I'm looking for ideally in priority order * Solve algebra problems * Definition of relationships relatively straight forward * Rich support for latex formatting (not just writing encoded strings) Thanks!

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  • Why would Mathematica break normal scoping rules in Module?

    - by Davorak
    As was pointed out in a recent post scoping does not work as expected inside of Module. An example from that thread is: Module[{expr}, expr = 2 z; f[z_] = expr; f[7]] (*2 z$1776*) But the following works as almost as expected. Module[{expr}, expr = 2 z; Set@@{f[z_], expr}; f[7]] (*14*) What language design consideration made wolfram choose this functionality?

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  • What is the best way to find the period of a (repeating) list in Mathematica?

    - by Arnoud Buzing
    What is the best way to find the period in a repeating list? For example: a = {4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2} has repeat {4, 5, 1, 2, 3} with the remainder {4, 5, 1, 2} matching, but being incomplete. The algorithm should be fast enough to handle longer cases, like so: b = RandomInteger[10000, {100}]; a = Join[b, b, b, b, Take[b, 27]] The algorithm should return $Failed if there is no repeating pattern like above.

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  • Parsing and generating JSON

    - by Pillsy
    Mathematica's list of built-in formats is pretty extensive; however, JSON is not on that list. Is there an existing solution for generating and parsing JSON in Mathematica, or are we going to have to roll our own solution?

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  • AbsoluteTime with numeric argument behaves strangely.

    - by dreeves
    This is strange: DateList@AbsoluteTime[596523] returns {2078, 7, 2, 2, 42, 9.7849} But DateList@AbsoluteTime[596524] returns {1942, 5, 26, 20, 28, 39.5596} The question: What's going on? Note that AbsoluteTime with a numeric argument is undocumented. (I think I now know what it's doing but figured this is useful to have as a StackOverflow question for future reference; and I'm curious if there's some reason for that magic 596523 number.) PS: I encountered this when writing these utility functions for converting to and from unix time in Mathematica: (* Using Unix time (an integer) instead of Mathematica's AbsoluteTime... *) tm[x___] := AbsoluteTime[x] (* tm is an alias for AbsoluteTime. *) uepoch = tm[{1970}, TimeZone->0]; (* unixtm works analogously to tm. *) unixtm[x___] := Round[tm[x]-uepoch] (* tm & unixtm convert between unix & *) unixtm[x_?NumericQ] := Round[x-uepoch] (* mma epoch time when given numeric *) tm[t_?NumericQ] := t+uepoch (* args. Ie, they're inverses. *)

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  • Nested WHILE loops not acting as expected - Javascript / Google Apps Script

    - by dthor
    I've got a function that isn't acting as intended. Before I continue, I'd like preface this with the fact that I normally program in Mathematica and have been tasked with porting over a Mathematica function (that I wrote) to JavaScript so that it can be used in a Google Docs spreadsheet. I have about 3 hours of JavaScript experience... The entire (small) project is calculating the Gross Die per Wafer, given a wafer and die size (among other inputs). The part that isn't working is where I check to see if any corner of the die is outside of the effective radius, Reff. The function takes a list of X and Y coordinates which, when combined, create the individual XY coord of the center of the die. That is then put into a separate function "maxDistance" that calculates the distance of each of the 4 corners and returns the max. This max value is checked against Reff. If the max is inside the radius, 1 is added to the die count. // Take a list of X and Y values and calculate the Gross Die per Wafer function CoordsToGDW(Reff,xSize,ySize,xCoords,yCoords) { // Initialize Variables var count = 0; // Nested loops create all the x,y coords of the die centers for (var i = 0; i < xCoords.length; i++) { for (var j = 0; j < yCoords.length, j++) { // Add 1 to the die count if the distance is within the effective radius if (maxDistance(xCoords[i],yCoords[j],xSize,ySize) <= Reff) {count = count + 1} } } return count; } Here are some examples of what I'm getting: xArray={-52.25, -42.75, -33.25, -23.75, -14.25, -4.75, 4.75, 14.25, 23.75, 33.25, 42.75, 52.25, 61.75} yArray={-52.5, -45.5, -38.5, -31.5, -24.5, -17.5, -10.5, -3.5, 3.5, 10.5, 17.5, 24.5, 31.5, 38.5, 45.5, 52.5, 59.5} CoordsToGDW(45,9.5,7.0,xArray,yArray) returns: 49 (should be 72) xArray={-36, -28, -20, -12, -4, 4, 12, 20, 28, 36, 44} yArray={-39, -33, -27, -21, -15, -9, -3, 3, 9, 15, 21, 27, 33, 39, 45} CoordsToGDW(32.5,8,6,xArray,yArray) returns: 39 (should be 48) I know that maxDistance() is returning the correct values. So, where's my simple mistake? Also, please forgive me writing some things in Mathematica notation... Edit #1: A little bit of formatting. Edit #2: Per showi, I've changed WHILE loops to FOR loops and replaced <= with <. Still not the right answer. It did clean things up a bit though... Edit #3: What I'm essentially trying to do is take [a,b] and [a,b,c] and return [[a,a],[a,b],[a,c],[b,a],[b,b],[b,c]]

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  • Add gridlines to a output plot in Mathemaitca

    - by xslittlegrass
    I'm trying to add gridlines to a output density plot in Mathematica. The plot is generated by a long calculation in Mathematica and when I do the plot I forget to add the Mesh-True options. I don't want to do all the calculation and generate the plot again since it takes a long time. Is that possible to add the gridlines or mesh lines to plot ONLY using the output plot at hand? For example, If I have a plot p. Is it possible to add the mesh lines ONLY manipulate p? In a ordinary one dimensional plot, this will work p1 = Plot[Sin[x], {x, -3, 3}]; Insert[p1, GridLines -> Automatic, -1] But when I try the density plot, it seems the gridlines is always under the plot, and can be seen only at the image margin area. p2 = DensityPlot[Sin[x + y^2], {x, -3, 3}, {y, -2, 2}, PlotRangePadding -> 0.2]; Insert[p2, GridLines -> Automatic, -1] Updata The Mesh option on the output plot will not work because Mesh is not a options of a Graphics: Show[p2,Mesh->True] will give a message "an unrecoginzed option name(Mesh) was encountered while rendering a Graphics" Thanks.

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  • Complex Calculations

    - by mson
    What are the best tools (most efficient) available in .NET (C#) for calculating: integrals partial derivatives other non-trivial math Can people please comment on Mathematica and Matlab and their integration into C#?

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  • Web UI for inputting a function from the reals to the reals, such as a probability distribution.

    - by dreeves
    I would like a web interface for a user to describe a one-dimensional real-valued function. I'm imagining the user being presented with a blank pair of axes and they can click anywhere to create points that are thick and draggable. Double-clicking a point, let's say, makes it disappear. The actual function should be shown in real time as an interpolation of the user-supplied points. Here's what this looks like implemented in Mathematica (though of course I'm looking for something in javascript):

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  • posmax: like argmax but gives the position(s) of the element x for which f[x] is maximal

    - by dreeves
    Mathematica has a built-in function ArgMax for functions over infinite domains, based on the standard mathematical definition. The analog for finite domains is a handy utility function. Given a function and a list (call it the domain of the function), return the element(s) of the list that maximize the function. Here's an example of finite argmax in action: http://stackoverflow.com/questions/471029/canonicalize-nfl-team-names/472213#472213 And here's my implementation of it (along with argmin for good measure): (* argmax[f, domain] returns the element of domain for which f of that element is maximal -- breaks ties in favor of first occurrence. *) SetAttributes[{argmax, argmin}, HoldFirst]; argmax[f_, dom_List] := Fold[If[f[#1]>=f[#2], #1, #2]&, First[dom], Rest[dom]] argmin[f_, dom_List] := argmax[-f[#]&, dom] First, is that the most efficient way to implement argmax? What if you want the list of all maximal elements instead of just the first one? Second, how about the related function posmax that, instead of returning the maximal element(s), returns the position(s) of the maximal elements?

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  • An efficient code to determine if a set is a subset of another set

    - by Edward
    I am looking for an efficient way to determine if a set is a subset of another set in Matlab or Mathematica. Example: Set A = [1 2 3 4] Set B = [4 3] Set C = [3 4 1] Set D = [4 3 2 1] The output should be: Set A Sets B and C belong to set A because A contains all of their elements, therefore, they can be deleted (the order of elements in a set doesn't matter). Set D has the same elements as set A and since set A precedes set D, I would like to simply keep set A and delete set D. So there are two essential rules: 1. Delete a set if it is a subset of another set 2. Delete a set if its elements are the same as those of a preceding set My Matlab code is not very efficient at doing this - it mostly consists of nested loops. Suggestions are very welcome! Additional explanation: the issue is that with a large number of sets there will be a very large number of pairwise comparisons.

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  • An efficient code to determine if a set is a subset of another set

    - by Edward
    I am looking for an efficient way to determine if a set is a subset of another set in Matlab or Mathematica. Example: Set A = [1 2 3 4] Set B = [4 3] Set C = [3 4 1] Set D = [4 3 2 1] The output should be: Set A Sets B and C belong to set A because A contains all of their elements, therefore, they can be deleted (the order of elements in a set doesn't matter). Set D has the same elements as set A and since set A precedes set D, I would like to simply keep set A and delete set D. So there are two essential rules: 1. Delete a set if it is a subset of another set 2. Delete a set if its elements are the same as those of a preceding set My Matlab code is not very efficient at doing this - it mostly consists of nested loops. Suggestions are very welcome! Additional explanation: the issue is that with a large number of sets there will be a very large number of pairwise comparisons.

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  • How to kill slave kernel securely?

    - by Alexey Popkov
    Hello, LinkClose[link] "does not necessarily terminate the program at the other end of the connection" as it is said in the Documentation. Is there a way to kill the process of the slave kernel securely? EDIT: In really I need a function in Mathematica that returns only when the process of the slave kernel has already killed and its memory has already released. Both LinkInterrupt[link, 1] and LinkClose[link] do not wait while the slave kernel exits. At this moment the only such function is seemed to be killProc[procID] function I had showed in one of answers at this page. But is there a built-in analog?

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  • Running Mathimatica-5 remotely

    - by oxinabox.ucc.asn.au
    Ok, I have Mathmatica 5 - a powerful CAS. I have a cheap netbook, wich not olny is too slow to run mathmatica on, I doubt it has the harddrive space. I do however have remote access to a number of very powerful computers, (most of wich run variose linuxes, but one of which is windows server 2008) Mostly over SSH but other protocols can be arraged for some, i'm sure. (I might even be able to remote desktop the windows server 2008) So I'ld like to install Mathmatica onto one of these machine and then run it remotely. Either from the command line via putty or via some other method. I glanced through the mathmatical documentaion and read soemthing about using some MathLink program, wich linkes the front end istalled on my computer to a remote kernal. Anyone have any expirience with this? I'm not sure if this belongs here or in SuperUser.

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