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  • C++ a class with an array of structs, without knowing how large an array I need

    - by Dominic Bou-Samra
    New to C++, and for that matter OO programming. I have a class with fields like firstname, age, school etc. I need to be able to store other information like for instance, where they have travelled, and what year it was in. I cannot declare another class specifically to hold travelDestination and what year, so I think a struct might be best. This is just an example: struct travel { string travelDest; string year; }; The issue is people are likely to have travelled different amounts. I was thinking of just having an array of travel structs to hold the data. But how do I create a fixed sized array to hold them, without knowing how big I need it to be? Perhaps I am going about this the completely wrong way, so any suggestions as to a better way would be appreciated.

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  • Cumulative +1/-1 Cointoss crashes on 1000 iterations. Please advise; c++ boost random libraries

    - by user1731972
    following some former advice Multithreaded application, am I doing it right? I think I have a threadsafe number generator using boost, but my program crashes when I input 1000 iterations. The output .csv file when graphed looks right, but I'm not sure why it's crashing. It's using _beginthread, and everyone is telling me I should use the more (convoluted) _beingthreadex, which I'm not familiar with. If someone could recommend an example, I would greatly appreciate it. Also... someone pointed out I should be applying a second parameter to my _beginthread for the array counting start positions, but I have no idea how to pass more than one parameter, other than attempting to use a structure, and I've read structure's and _beginthread don't get along (although, I could just use the boost threads...) #include <process.h> #include <windows.h> #include <iostream> #include <fstream> #include <time.h> #include <random> #include <boost/random.hpp> //for srand48_r(time(NULL), &randBuffer); which doesn't work #include <stdio.h> #include <stdlib.h> //#include <thread> using namespace std; using namespace boost; using namespace boost::random; void myThread0 (void *dummy ); void myThread1 (void *dummy ); void myThread2 (void *dummy ); void myThread3 (void *dummy ); //for random seeds void initialize(); //from http://stackoverflow.com/questions/7114043/random-number-generation-in-c11-how-to-generate-how-do-they-work uniform_int_distribution<> two(1,2); typedef std::mt19937 MyRNG; // the Mersenne Twister with a popular choice of parameters uint32_t seed_val; // populate somehow MyRNG rng1; // e.g. keep one global instance (per thread) MyRNG rng2; // e.g. keep one global instance (per thread) MyRNG rng3; // e.g. keep one global instance (per thread) MyRNG rng4; // e.g. keep one global instance (per thread) //only needed for shared variables //CRITICAL_SECTION cs1,cs2,cs3,cs4; // global int main() { ofstream myfile; myfile.open ("coinToss.csv"); int rNum; long numRuns; long count = 0; int divisor = 1; float fHolder = 0; long counter = 0; float percent = 0.0; //? //unsigned threadID; //HANDLE hThread; initialize(); HANDLE hThread[4]; const int size = 100000; int array[size]; printf ("Runs (uses multiple of 100,000) "); cin >> numRuns; for (int a = 0; a < numRuns; a++) { hThread[0] = (HANDLE)_beginthread( myThread0, 0, (void*)(array) ); hThread[1] = (HANDLE)_beginthread( myThread1, 0, (void*)(array) ); hThread[2] = (HANDLE)_beginthread( myThread2, 0, (void*)(array) ); hThread[3] = (HANDLE)_beginthread( myThread3, 0, (void*)(array) ); //waits for threads to finish before continuing WaitForMultipleObjects(4, hThread, TRUE, INFINITE); //closes handles I guess? CloseHandle( hThread[0] ); CloseHandle( hThread[1] ); CloseHandle( hThread[2] ); CloseHandle( hThread[3] ); //dump array into calculations //average array into fHolder //this could be split into threads as well for (int p = 0; p < size; p++) { counter += array[p] == 2 ? 1 : -1; //cout << array[p] << endl; //cout << counter << endl; } //this fHolder calculation didn't work //fHolder = counter / size; //so I had to use this cout << counter << endl; fHolder = counter; fHolder = fHolder / size; myfile << fHolder << endl; } } void initialize() { //seed value needs to be supplied //rng1.seed(seed_val*1); rng1.seed((unsigned int)time(NULL)); rng2.seed(((unsigned int)time(NULL))*2); rng3.seed(((unsigned int)time(NULL))*3); rng4.seed(((unsigned int)time(NULL))*4); }; void myThread0 (void *param) { //EnterCriticalSection(&cs1); //aquire the critical section object int *i = (int *)param; for (int x = 0; x < 25000; x++) { //doesn't work, part of merssene twister //i[x] = next(); i[x] = two(rng1); //original srand //i[x] = rand() % 2 + 1; //doesn't work for some reason. //uint_dist2(rng); //i[x] = qrand() % 2 + 1; //cout << i[x] << endl; } //LeaveCriticalSection(&cs1); // release the critical section object } void myThread1 (void *param) { //EnterCriticalSection(&cs2); //aquire the critical section object int *i = (int *)param; for (int x = 25000; x < 50000; x++) { //param[x] = rand() % 2 + 1; i[x] = two(rng2); //i[x] = rand() % 2 + 1; //cout << i[x] << endl; } //LeaveCriticalSection(&cs2); // release the critical section object } void myThread2 (void *param) { //EnterCriticalSection(&cs3); //aquire the critical section object int *i = (int *)param; for (int x = 50000; x < 75000; x++) { i[x] = two(rng3); //i[x] = rand() % 2 + 1; //cout << i[x] << endl; } //LeaveCriticalSection(&cs3); // release the critical section object } void myThread3 (void *param) { //EnterCriticalSection(&cs4); //aquire the critical section object int *i = (int *)param; for (int x = 75000; x < 100000; x++) { i[x] = two(rng4); //i[x] = rand() % 2 + 1; //cout << i[x] << endl; } //LeaveCriticalSection(&cs4); // release the critical section object }

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  • PHP search multidimensional array for value, then place that element at start of array

    - by BobFlemming
    I need to search this array: cars - [0] -make : Ford -model: Escort -year: 1991 [1] -make: Honda -model: Civic -year: 1996 [2] -make: Vauxhall -model: Astra -year: 1972 And if (for example) the model is "Civic" , place that 'car' at position 0. So the end array would be like: cars - [0] -make: Honda -model: Civic -year: 1996 [1] -make : Ford -model: Escort -year: 1991 [2] -make: Vauxhall -model: Astra -year: 1972 I've tried some usort variations: function typeSort($a, $b) { if ($a['model'] == 'Civic' ) { return 0; } return ($a['model'] < $b['model']) ? -1 : 1; } but this is just returning 1

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  • Split a sting array into a number array in javascript

    - by Wesley Skeen
    I am reading a value from a dropdown list depending on what option is selected. I am using jqPlot to graph the values. jqPlot expects an array of values like [91, 6, 2, 57, 29, 40, 95] but when I read the value in from the dropdown box it is coming in as a whole string "[91, 6, 2, 57, 29, 40, 95]" I tried splitting it but I got ["91", "6", "2", "57", "29", "40", "95"] which wont display the graph correctly. Is there anybody that has encountered something like this before and what can I do to make my values convert into a number array. Thanks for any help

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  • Array or array element in C?

    - by user3646717
    I'm reading a book about C programming, and I'm not sure whether there is an error in the book or not. Its about arrays and has the following array example: Then it says: The following statements sets all the elements in row 2 of array to zero: for( column = 0; column <= 3; column++) a[ 2 ][ column ] = 0; The preceding for statement is equivalent to the assignment statements: a[ 2 ][ 0 ] = 0; a[ 2 ][ 1 ] = 0; a[ 2 ][ 2 ] = 0; a[ 2 ][ 3 ] = 0; Shouldn't it say "The following statements sets all the elements in row 1 to zero"?. Because if I say a[ 3 ] I am talking about the row 2, if I say a[ 2 ] I am talking about row 1 and if I say a[ 1 ] I am talking about row 0.

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  • VC9 C1083 Cannot open include file: 'boost...' after trying to abstract an include dependency

    - by ronivek
    Hey, So I've been working on a project for the past number of weeks and it uses a number of Boost libraries. In particular I'm using the boost::dynamic_bitset library quite extensively. I've had zero issues up until now; but tonight I discovered a dependency between some includes which I had to resolve; and I tried to do so by providing an abstract callback class. Effectively I now have the following: First include... class OtherClassCallback { public: virtual int someOtherMethod() const = 0; }; class SomeClass { public: void someMethod(OtherClassCallback *oc) { ... oc->someOtherMethod(); ... } }; Second include... #include "SomeClass.h" class SomeOtherClass : public OtherClassCallback { public: int someOtherMethod() const { return this->someInt; } }; Here is the issue; ever since I implemented this class I'm now getting the following error: fatal error C1083: Cannot open include file: 'boost/dynamic_bitset/dynamic_bitset.hpp': No such file or directory Now I'm getting no other compiler errors; and it's a pretty substantial project. My include paths and so on are perfect; my files are fully accessible and removing the changes fixes the issue. Does anyone have any idea what might be going on? I'm compiling to native Windows executables in VS9. I should confess that I'm very inexperienced with C++ in general so go easy on me if it's something horribly straightforward; I can't figure it out.

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  • Drawing using Dynamic Array and Buffer Object

    - by user1905910
    I have a problem when creating the vertex array and the indices array. I don't know what really is the problem with the code, but I guess is something with the type of the arrays, can someone please give me a light on this? #define GL_GLEXT_PROTOTYPES #include<GL/glut.h> #include<iostream> using namespace std; #define BUFFER_OFFSET(offset) ((GLfloat*) NULL + offset) const GLuint numDiv = 2; const GLuint numVerts = 9; GLuint VAO; void display(void) { enum vertex {VERTICES, INDICES, NUM_BUFFERS}; GLuint * buffers = new GLuint[NUM_BUFFERS]; GLfloat (*squareVerts)[2] = new GLfloat[numVerts][2]; GLubyte * indices = new GLubyte[numDiv*numDiv*4]; GLuint delta = 80/numDiv; for(GLuint i = 0; i < numVerts; i++) { squareVerts[i][1] = (i/(numDiv+1))*delta; squareVerts[i][0] = (i%(numDiv+1))*delta; } for(GLuint i=0; i < numDiv; i++){ for(GLuint j=0; j < numDiv; j++){ //cada iteracao gera 4 pontos #define NUM_VERT(ii,jj) ((ii)*(numDiv+1)+(jj)) #define INDICE(ii,jj) (4*((ii)*numDiv+(jj))) indices[INDICE(i,j)] = NUM_VERT(i,j); indices[INDICE(i,j)+1] = NUM_VERT(i,j+1); indices[INDICE(i,j)+2] = NUM_VERT(i+1,j+1); indices[INDICE(i,j)+3] = NUM_VERT(i+1,j); } } glGenVertexArrays(1, &VAO); glBindVertexArray(VAO); glGenBuffers(NUM_BUFFERS, buffers); glBindBuffer(GL_ARRAY_BUFFER, buffers[VERTICES]); glBufferData(GL_ARRAY_BUFFER, sizeof(squareVerts), squareVerts, GL_STATIC_DRAW); glVertexPointer(2, GL_FLOAT, 0, BUFFER_OFFSET(0)); glEnableClientState(GL_VERTEX_ARRAY); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, buffers[INDICES]); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW); glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0,1.0,1.0); glDrawElements(GL_POINTS, 16, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0)); glutSwapBuffers(); } void init() { glClearColor(0.0, 0.0, 0.0, 0.0); gluOrtho2D((GLdouble) -1.0, (GLdouble) 90.0, (GLdouble) -1.0, (GLdouble) 90.0); } int main(int argv, char** argc) { glutInit(&argv, argc); glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE); glutInitWindowSize(500,500); glutInitWindowPosition(100,100); glutCreateWindow("myCode.cpp"); init(); glutDisplayFunc(display); glutMainLoop(); return 0; } Edit: The problem here is that drawing don't work at all. But I don't get any error, this just don't display what I want to display. Even if I put the code that make the vertices and put them in the buffers in a diferent function, this don't work. I just tried to do this: void display(void) { glBindVertexArray(VAO); glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0,1.0,1.0); glDrawElements(GL_POINTS, 16, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0)); glutSwapBuffers(); } and I placed the rest of the code in display in another function that is called on the start of the program. But the problem still

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  • java: Read text file and store the info in an array using scanner class

    - by Amateur
    Hi, I have a text file include Student Grades like Kim $ 40 $ 45 Jack $ 35 $ 40 I'm trying to read this data from the text file and store the information into an array list using Scanner Class could any one guied me to write the code correctly ? Here is what I have so far public class ReadStudentsGrade { public static void main(String[] args) throws IOException { ArrayList stuRec = new ArrayList(); File file = new File("c:\\StudentGrade.txt"); try { Scanner scanner = new Scanner(file).useDelimiter("$"); while (scanner.hasNextLine()) { String stuName = scanner.nextLine(); int midTirmGrade = scanner.nextInt(); int finalGrade = scanner.nextInt(); System.out.println(stuName + " " + midTirmGrade + " " + finalGrade); } } catch (FileNotFoundException e) { e.printStackTrace(); } }

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  • PHP: testing for existence of a cell in a multidimensional array

    - by gidireich
    Hi, I have an array with numerous dimensions. Want to test for existence of a cell. The below cascaded approach, will be for sure a safe way to do it: if (array_key_exists($arr, 'dim1Key')) if (array_key_exists($arr['dim1Key'], 'dim2Key')) if (array_key_exists($arr['dim1Key']['dim2Key'], 'dim3Key')) echo "cell exists"; But it there a simpler way? I'll go into more details about this: 1. Can I perform this check in one single statement? 2. Do I have to use array_key_exist or can I use something like isset? Will appreciate if someone explains when to use each and why Thanks Gidi

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  • Array of pointers in objective-c

    - by Justin
    I'm getting confused by pointers in objective-c. Basically I have a bunch of static data in my code. static int dataSet0[2][2] = {{0, 1}, {2, 3}}; static int dataSet1[2][2] = {{4, 5}, {6, 7}}; And I want to have an array to index it all. dataSets[0]; //Would give me dataSet0... What should the type of dataSets be, and how would I initialize it?

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  • how to build an accumulator array in matlab

    - by schwiz
    I'm very new to matlab so sorry if this is a dumb question. I have to following matrices: im = imread('image.jpg'); %<370x366 double> [y,x] = find(im); %x & y both <1280x1 double> theta; %<370x366 double> computed from gradient of image I can currently plot points one at a time like this: plot(x(502) + 120*cos(theta(y(502),x(502))),y(502) + 120*sin(theta(y(502),x(502))),'*b'); But what I want to do is some how increment an accumulator array, something like this: acc = zeros(size(im)); acc(y,x) = acc(x + 120*cos(theta(y,x)),y + 120*sin(theta(y,x)),'*b')) + 1; It would be nice if the 120 could actually be another matrix containing different radius values as well.

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  • Can't make an array in C#

    - by Josh
    I'm trying to make a dynamic array in C# but I get an annoying error message. Here's my code: private void Form1_Load(object sender, EventArgs e) { int[] dataArray; Random random = new Random(); for (int i = 0; i < random.Next(1, 10); i++) { dataArray[i] = random.Next(1, 1000); } } And the error: Use of unassigned local variable 'dataArray' This is just baffling my mind. I came from VB, so please me gentle, lol. Cheers.

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  • mutidimensional array from javascript/jquery to ruby/sinatra

    - by user199368
    Hi, how do I pass a 2-dimensional array from javascript to ruby, please? I have this on client side: function send_data() { var testdata = { "1": { "name": "client_1", "note": "bigboy" }, "2": { "name": "client_2", "note": "smallboy" } } console.log(testdata); $.ajax({ type: 'POST', url: 'test', dataType: 'json', data: testdata }); } and this on server side: post '/test' do p params end but I can't get it right. The best I could get on server side is something like {"1"=>"[object Object]", "2"=>"[object Object]"} I tried to add JSON.stringify on client side and JSON.parse on server side, but the first resulted in {"{\"1\":{\"name\":\"client_1\",\"note\":\"bigboy\"},\"2\":{\"name\":\"client_2\",\"note\":\"smallboy\"}}"=>nil} while the latter has thrown a TypeError - can't convert Hash into String. Could anyone help, or maybe post a short snippet of correct code, please? Thank you

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  • Ruby - Call method passing values of array as each parameter

    - by Markus Orreilly
    I'm currently stuck on this problem. I've hooked into the method_missing function in a class I've made. When a function is called that doesn't exist, I want to call another function I know exists, passing the args array as all of the parameters to the second function. Does anyone know a way to do this? For example, I'd like to do something like this: class Blah def valid_method(p1, p2, p3, opt=false) puts "p1: #{p1}, p2: #{p2}, p3: #{p3}, opt: #{opt.inspect}" end def method_missing(methodname, *args) if methodname.to_s =~ /_with_opt$/ real_method = methodname.to_s.gsub(/_with_opt$/, '') send(real_method, args) # <-- this is the problem end end end b = Blah.new b.valid_method(1,2,3) # output: p1: 1, p2: 2, p3: 3, opt: false b.valid_method_with_opt(2,3,4) # output: p1: 2, p2: 3, p3: 4, opt: true (Oh, and btw, the above example doesn't work for me)

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  • Java: matching two different type of array

    - by sling
    Hi, I am doing a password login that requires me to match two array: User and Pass. If user key in "mark" and "pass", it should show successfully. However I have trouble with the String[] input = pass.getPassword(); and the matching of the two arrays. String[] User = {"mark", "susan", "bobo"}; String[] Pass = {"pass", "word", "password"}; String[] input = pass.getPassword(); if(Pass.length == input.length && user.getText().equals(User)) { lblstat.setForeground(Color.GREEN); lblstat.setText("Successful"); } else { lblstat.setForeground(Color.RED); lblstat.setText("Failed"); }

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  • Mysql IN clause, php array

    - by robert knobulous
    I know that this has been asked and answered before, but for the life of me I cannot find where I am going wrong. My code is below. $backa = array("1", "7", "8", "9", "12"); $backaa = implode(",", $backa); /* code to create connection object $wkHook */ $getOpt=$wkHook->prepare("select movementId, movementName from Movement where movementId IN ($backaa) order by movementName asc"); $getOpt->execute(); $getOpt->store_result($id, $name); Every time I run this I get one of two errors depending upon how I use the $backaa variable. More often than not I get a call to a non-object error indicating that $getOpt is not a proper Mysql query. I have tried every fashion of quoting, bracketing, etc for the $backaa variable but it's just not working for me. What obvious thing am I missing?

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  • perl array of hashes sorting

    - by srk
    use strict; my @arr; $arr[0][0]{5} = 16; $arr[0][1]{6} = 11; $arr[0][2]{7} = 25; $arr[0][3]{8} = 31; $arr[0][4]{9} = 16; $arr[0][5]{10} = 17; sort the array based on hash values so this should change to $arr[0][0]{6} = 11; $arr[0][1]{9} = 16; $arr[0][2]{5} = 16; $arr[0][3]{10} = 17; $arr[0][4]{7} = 25; $arr[0][5]{8} = 31; first sort on values in the hash.. when the values are same reverse sort based on keys... Please tell me how to do this.. Thank you

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  • PHP 2D Array to MySQL Database

    - by Ashley Ward
    I have a PHP 2D array, many keys, each with one value, I need to put this into a MySQL database. The database has 8 fields. Eg. Field1, Field2, Field3, etc. I am trying to ensure value1 => field1, value2 =>field2, value3 => field3 and so on, when one record is full (i.e. after 8 values) a new record should be created for the next 8 values and so on. I am aware that the 1st, 9th, 17th, 26th values etc, will need an insert statement and the intermediate values will be an update statement. What is the best way of going about this?

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  • Finding indexes of each element in a multidimensional array in ruby

    - by Shreyas Satish
    Eg :a=[["hello", "world"], ["good", "lord"], ["hello", "lord"]] I need to find and record the indexes of each word with respect to the super-array. i.e hello => 0,2 world => 0 lord => 1,2. here's my shot ,but its very amateurish and lengthy. all_tokens=tokens.flatten all_tokens.each do|keyword| tokens.each do|token_array| if token_array.include?keyword x << i end i=i+1 end y[k] = x.clone y=y.clear end

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  • Pascal error with array

    - by Donator
    program s;       type info = record                    name, surname: string;                    min, sec: integer;       end;       arrays = array[2..50] of info;       var A: arrays; begin       A[1].name := 'name'; end. What is wrong with that? It gives me range check error and I have no idea what is that.

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  • C# assign char and char array to string?

    - by Bopha
    char character = 'c'; string str = null; str = character.ToString();//this is ok char[] arrayChar = { 'a', 'b', 'c', 'd' }; string str2 = null; str2 = string.Copy(arrayChar.ToString());//this is not ok str2 = arrayChar.ToString();//this is not ok. I'm trying to converting char array to string, but the last two attempts don't work. Other source I found and they have to create new string type, but I don't know why. Can someone give me little explaination, thanks.

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  • Search object array for matching possible multiple values using different comparison operators

    - by Sparkles
    I have a function to search an array of objects for a matching value using the eq operator, like so: sub find { my ( $self, %params ) = @_; my @entries = @{ $self->{_entries} }; if ( $params{filename} ) { @entries = grep { $_->filename eq $params{filename} } @entries; } if ( $params{date} ) { @entries = grep { $_->date eq $params{date} } @entries; } if ( $params{title} ) { @entries = grep { $_->title eq $params{title} } @entries; } .... I wanted to also be able to pass in a qr quoted variable to use in the comparison instead but the only way I can think of separating the comparisons is using an if/else block, like so: if (lc ref($params{whatever}) eq 'regexp') { #use =~ } else { #use eq } Is there a shorter way of doing it? Because of reasons beyond my control I'm using Perl 5.8.8 so I can't use the smart match operator. TIA

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  • remove duplicates from object array data java

    - by zahir hussain
    hi i want to know how to remove duplicates in object. for example cat c[] = new cat[10]; c[1].data = "ji"; c[2].data = "pi"; c[3].data = "ji"; c[4].data = "lp"; c[5].data = "ji"; c[6].data = "pi"; c[7].data = "jis"; c[8].data = "lp"; c[9].data = "js"; c[10].data = "psi"; i would like to remove the duplicates value from object array. thanks and advance

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  • Numpy modify array in place?

    - by User
    I have the following code which is attempting to normalize the values of an m x n array (It will be used as input to a neural network, where m is the number of training examples and n is the number of features). However, when I inspect the array in the interpreter after the script runs, I see that the values are not normalized; that is, they still have the original values. I guess this is because the assignment to the array variable inside the function is only seen within the function. How can I do this normalization in place? Or do I have to return a new array from the normalize function? import numpy def normalize(array, imin = -1, imax = 1): """I = Imin + (Imax-Imin)*(D-Dmin)/(Dmax-Dmin)""" dmin = array.min() dmax = array.max() array = imin + (imax - imin)*(array - dmin)/(dmax - dmin) print array[0] def main(): array = numpy.loadtxt('test.csv', delimiter=',', skiprows=1) for column in array.T: normalize(column) return array if __name__ == "__main__": a = main()

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