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  • How do I efficiently locate key-value pairs in a multi-dimensional PHP array?

    - by Kyle Noland
    I have an array in PHP as a result of the following query to a Wordpress database: SELECT * FROM wp_postmeta WHERE post_id = :id I am returned a multidimensional array that looks like this: Array ( [0] => Array ( [meta_id] => 380 [post_id] => 72 [meta_key] => _edit_last [meta_value] => 1 ) ... etc. What is the best way to find a particular key-value pair in this array? For instance, how would I located the row where [meta_key] = event_name so that I can extract that same row's [meta_value] value into a PHP variable? I realize I could turn this into many individual MySQL queries. Does anyone have an opinion of the efficiency of doing 10 SQL queries in a row rather than searching the array 10 times? I would think since the array is in memory, that will be the fastest method to find the values I need. Alternatively, is there a better way to query the database from the beginning so that my result set is formatted in a way that is easier to search?

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  • Vacancy Tracking Algorithm implementation in C++

    - by Dave
    I'm trying to use the vacancy tracking algorithm to perform transposition of multidimensional arrays in C++. The arrays come as void pointers so I'm using address manipulation to perform the copies. Basically, there is an algorithm that starts with an offset and works its way through the whole 1-d representation of the array like swiss cheese, knocking out other offsets until it gets back to the original one. Then, you have to start at the next, untouched offset and do it again. You repeat until all offsets have been touched. Right now, I'm using a std::set to just fill up all possible offsets (0 up to the multiplicative fold of the dimensions of the array). Then, as I go through the algorithm, I erase from the set. I figure this would be fastest because I need to randomly access offsets in the tree/set and delete them. Then I need to quickly find the next untouched/undeleted offset. First of all, filling up the set is very slow and it seems like there must be a better way. It's individually calling new[] for every insert. So if I have 5 million offsets, there's 5 million news, plus re-balancing the tree constantly which as you know is not fast for a pre-sorted list. Second, deleting is slow as well. Third, assuming 4-byte data types like int and float, I'm using up actually the same amount of memory as the array itself to store this list of untouched offsets. Fourth, determining if there are any untouched offsets and getting one of them is fast -- a good thing. Does anyone have suggestions for any of these issues?

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  • Can I access type int (*)[] with [][]?

    - by Framester
    Hi coming from this question "What does (int (*)[])var1 stand for?" I tried to access the result of the cast like a multidimensional array. But I get following error: "assignment from incompatible pointer type" followed by a segmentation fault. I tried also some other variations, but none of them worked. How can I access the elements in var1 in the function example directly? Thank you! #include <stdlib.h> int i(int n,int m,int var1[n][m]) { var1[0][0]=5; return var1[0][0]; } int example() { int *var1 = malloc(100); // works int var2; var2 = i(10,10,(int (*)[])var1); printf("var2=%i",var2); //doesn't work I int *var3; var3=(int (*)[])var1; //"assignment from incompatible pointer type" printf("var3[0][0]=%i",var3[0][0]); //doesn't work II int *var4; var4=var1; printf("var4[0][0]=%i",var4[0][0]); //" error: subscripted value is neither array nor pointer" //doesn't work III int **var5; var5=var1; printf("var5[0][0]=%i",var5[0][0]); // assignment from incompatible pointer type return(1); } int main(){ int a; a=example(); return(1); }

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  • jQuery accessing objects

    - by user1275268
    I'm trying to access the values of an object from a function I created with a callback, but have run into some trouble. I'm still fairly new at jQuery/javascript. I call the function as follows: siteDeps(id,function(data){ $.each(data,function(key,val) { console.log(key); console.log(val); }); }); The function runs 5 ajax queries from XML data and returns data as an multidimensional object; here is a excerpt showing the meat of it: function siteDeps(id,callback) { var result = { sitecontactid : {}, siteaddressid : {}, sitephoneid : {}, contactaddressid : {}, contactphoneid : {} }; ...//.... var url5 = decodeURIComponent("sql2xml.php?query=xxxxxxxxxxx"); $.get(url5, function(data){ $(data).find('ID').each(function(i){ result.delsitephoneid[i] = $(this).text(); }); }); callback(result); } The console.log output shows this: sitecontactid Object 0: "2" 1: "3" __proto__: Object siteaddressid Object 0: "1" __proto__: Object sitephoneid Object 0: "1" 1: "5" 2: "54" __proto__: Object contactaddressid Object 0: "80" __proto__: Object contactphoneid Object 0: "6" __proto__: Object How can I extract the callback data in a format I can use, for instance sitephoneid: "1","5","54" Or is there a better/simpler way to do this? Thanks in advance.

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  • foreach loop corrupting my array?

    - by WmasterJ
    Explanation I have a multidimensional array that is iterated over to created a categorized view of people with different research interests. The main array look something like this: Array ( ... ['Cell Biology'] => Array(4 elements) ['Molecular'] => Array(6 elements) ['Biology Education'] => Array(14 elements) ['Plant Biology'] => Array(19 elements) <--- Last element in array ) I know that the entire array is intact and correctly structured. The only information that is inside these array is an user id, like so: Array ('Plant Biology') 19 elements ( [0] => 737 [1] => 742 [2] => 748 ... ) My problem is that after i run the main array through a foreach loop the last 'sub-array' gets messed up. By messed up I mean that what you see about instead look like: String (13 characters) 'Plant Biology' This is without doing at all anything inside the loop with to the array that gets corrupted. Any tips to what it might be? PHP Code // ---> Array is OK here echo "<h2>Research divided</h2>"; // Loop areas and list them in 2 columns foreach($research['areas'] as $area => $areaArray) { // ---> Here it is already corrupted $count = count($areaArray); if($count > 0) { echo "<h3>$area</h3><hr/>"; echo "<table class='area_list'><tr>"; // Loop users within areas, divided up in 2 columns for($i=0 ; $i<$count ; $i++) { $uid = $areaArray[$i]; echo "<li>$uid</li>"; } echo "</tr></table>"; } }

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  • iPhone game reading plist file and looping through multi dimensional array.

    - by Fulvio
    I have a question regarding an iPhone game I'm developing. At the moment, below is the code I'm using to currently I loop through my multidimensional array and position bricks accordingly on my scene. Instead of having multiple two dimensional arrays within my code as per the following (gameLevel1). Ideally, I'd like to read from a .plist file within my project and loop through the values in that instead. Please take into account that I'd like to have more than one level within my game (possibly 20) so my .plist file would have to have some sort of separator line item to determine what level I want to render. I was then thinking of having some sort of method that I call and that method would take the level number I'm interested in rendering. e.g. Method? +(void)renderLevel:(NSString levelNumber); e.g. .plist file? #LEVEL_ONE# 0,0,0,0,0,0,0,0,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,1,1,1,1,1,1,1,0 0,0,0,0,0,0,0,0,0 #LEVEL_TWO# 1,0,0,0,0,0,0,0,1 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 0,1,1,1,1,1,1,1,0 1,1,1,1,1,1,1,1,1 0,1,1,1,1,1,1,1,0 1,1,1,1,1,1,1,1,1 0,1,1,1,1,1,1,1,0 1,1,1,1,1,1,1,1,1 0,1,1,1,1,1,1,1,0 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 1,1,1,1,1,1,1,1,1 1,0,0,0,0,0,0,0,1 Code that I'm currently using: int gameLevel[17][9] = { { 0,0,0,0,0,0,0,0,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,1,1,1,1,1,1,1,0 }, { 0,0,0,0,0,0,0,0,0 } }; for (int row=0; row < 17; row++) { for (int col=0; col < 9; col++) { thisBrickValue = gameLevel[row][col]; xOffset = 35 * floor(col); yOffset = 22 * floor(row); switch (thisBrickValue) { case 0: brick = [[CCSprite spriteWithFile:@"block0.png"] autorelease]; break; case 1: brick = [[CCSprite spriteWithFile:@"block1.png"] autorelease]; break; } brick.position = ccp(xOffset, yOffset); [self addChild:brick]; } }

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  • Output a php multi-dimensional array to a html table

    - by Fireflight
    I have been banging my head against the wall with this one for nearly a week now, and am no closer than I was the first day. I have a form that has 8 columns and a variable number of rows which I need to email to the client in a nicely formatted email. The form submits the needed fields as a multidimensional array. Rough example is below: <input name="order[0][topdiameter]" type="text" id="topdiameter0" value="1" size="5" /> <input name="order[0][bottomdiameter]" type="text" id="bottomdiameter0" value="1" size="5" /> <input name="order[0][slantheight]" type="text" id="slantheight0" value="1" size="5" /> <select name="order[0][fittertype]" id="fittertype0"> <option value="harp">Harp</option> <option value="euro">Euro</option> <option value="bulbclip">Regular</option> </select> <input name="order[0][washerdrop]" type="text" id="washerdrop0" value="1" size="5" /> <select name="order[0][fabrictype]" id="fabrictype"> <option value="linen">Linen</option> <option value="pleated">Pleated</option> </select> <select name="order[0][colours]" id="colours0"> <option value="beige">Beige</option> <option value="white">White</option> <option value="eggshell">Eggshell</option> <option value="parchment">Parchment</option> </select> <input name="order[0][quantity]" type="text" id="quantity0" value="1" size="5" /> This form is formatted in a table, and rows can be added to it dynamically. What I've been unable to do is get a properly formatted table out of the array. This is what I'm using now (grabbed from the net). <?php if (isset($_POST["submit"])) { $arr= $_POST['order'] echo '<table>'; foreach($arr as $arrs) { echo '<tr>'; foreach($arrs as $item) { echo "<td>$item</td>"; } echo '</tr>'; } echo '</table>; }; ?> This works perfectly for a single row of data. If I try submitting 2 or more rows from the form then one of the columns disappears. I'd like the table to be formatted as: | top | Bottom | Slant | Fitter | Washer | Fabric | Colours | Quantity | ------------------------------------------------------------------------ |value| value | value | value | value | value | value | value | with additional rows as needed. But, I can't find any examples that will generate that type of table! It seems like this should be something fairly straightforward, but I just can't locate an example that works the way I need it too.

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  • How to loop through a javascript object and check each key exists in a separate multidimensional object

    - by Paul Atkins
    I have 2 javascript objects and I am trying to loop through one object and check whether the key exists in a second multidimensional object going one level deeper each time. Here are the two objects var check = {'scope':'instance', 'item':'body', 'property': 'background'}; var values = {'instance': {'body' : {'background': '000000'}}}; b.map(check, function(key){ console.log(values[key]); }); How am I able to check 1 level deeper in the values object each time? What I am trying to do is check the values object as follows: 1st values['instance'] 2nd values['instance']['body'] 3rd values['instance']['body']['background'] Thanks

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  • Create a subarray reference in C# (using unsafe ?)

    - by Wam
    Hello there, I'm refactoring a library we currently use, and I'm faced with the following problem. We used to have the following stuff : class Blah { float[][] data; public float[] GetDataReference(int index) { return data[index]; } } For various reasons, I have replaced this jagged array version with a 1 dimensionnal array version, concatenating inner arrays. My question is : how can I still return a reference to a sub array of data ? class Blah { float[] data; int rows; public float[] GetDataReference(int index) { // Return a reference data from offset i to offset j; } } I was thinking that unsafe and pointers stuff may be of use, is it doable ?

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  • Variable number of two-dimensional arrays into one big array

    - by qlb
    I have a variable number of two-dimensional arrays. The first dimension is variable, the second dimension is constant. i.e.: Object[][] array0 = { {"tim", "sanchez", 34, 175.5, "bla", "blub", "[email protected]"}, {"alice", "smith", 42, 160.0, "la", "bub", "[email protected]"}, ... }; Object[][] array1 = { {"john", "sdfs", 34, 15.5, "a", "bl", "[email protected]"}, {"joe", "smith", 42, 16.0, "a", "bub", "[email protected]"}, ... }; ... Object[][] arrayi = ... I'm generating these arrays with a for-loop: for (int i = 0; i < filter.length; i++) { MyClass c = new MyClass(filter[i]); //data = c.getData(); } Where "filter" is another array which is filled with information that tells "MyClass" how to fill the arrays. "getData()" gives back one of the i number of arrays. Now I just need to have everything in one big two dimensional array. i.e.: Object[][] arrayComplete = { {"tim", "sanchez", 34, 175.5, "bla", "blub", "[email protected]"}, {"alice", "smith", 42, 160.0, "la", "bub", "[email protected]"}, ... {"john", "sdfs", 34, 15.5, "a", "bl", "[email protected]"}, {"joe", "smith", 42, 16.0, "a", "bub", "[email protected]"}, ... ... }; In the end, I need a 2D array to feed my Swing TableModel. Any idea on how to accomplish this? It's blowing my mind right now.

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  • how to reduce 2d array

    - by owca
    I have a 2d array, let's say like this : 2 0 8 9 3 0 -1 20 13 12 17 18 1 2 3 4 2 0 7 9 How to create an array reduced by let's say 2nd row and third column? 2 0 9 13 12 18 1 2 4 2 0 9

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  • Array Unique in two dimentional array in PHP

    - by Kaiser
    Hi I have an array that looks like this : Array ( [0] => Array ( [x] => 01 [y] => 244 ) [1] => Array ( [x] => 02 [y] => 244 ) [2] => Array ( [x] => 03 [y] => 244 ) [3] => Array ( [x] => 04 [y] => 243 ) [4] => Array ( [x] => 05 [y] => 243 ) [5] => Array ( [x] => 05 [y] => 244 ) [6] => Array ( [x] => 06 [y] => 242 ) [7] => Array ( [x] => 06 [y] => 243 ) [8] => Array ( [x] => 07 [y] => 243 ) [9] => Array ( [x] => 08 [y] => 243 ) [10] => Array ( [x] => 09 [y] => 242 ) [11] => Array ( [x] => 10 [y] => 244 ) [12] => Array ( [x] => 12 [y] => 243 ) [13] => Array ( [x] => 13 [y] => 243 ) [14] => Array ( [x] => 13 [y] => 243 ) [15] => Array ( [x] => 15 [y] => 243 ) ) x represent days and y values of a certain variable. I would like to display an array of unique days x ( last element ) and values y pragmatically. for example day 6 I have two y values but I want to display only the last one ( 243 ). Thanks for help

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  • Array Unique in two dimensional array in PHP

    - by Kaiser
    Hi I have an array that looks like this : Array ( [0] => Array ( [x] => 01 [y] => 244 ) [1] => Array ( [x] => 02 [y] => 244 ) [2] => Array ( [x] => 03 [y] => 244 ) [3] => Array ( [x] => 04 [y] => 243 ) [4] => Array ( [x] => 05 [y] => 243 ) [5] => Array ( [x] => 05 [y] => 244 ) [6] => Array ( [x] => 06 [y] => 242 ) [7] => Array ( [x] => 06 [y] => 243 ) [8] => Array ( [x] => 07 [y] => 243 ) [9] => Array ( [x] => 08 [y] => 243 ) [10] => Array ( [x] => 09 [y] => 242 ) [11] => Array ( [x] => 10 [y] => 244 ) [12] => Array ( [x] => 12 [y] => 243 ) [13] => Array ( [x] => 13 [y] => 243 ) [14] => Array ( [x] => 13 [y] => 243 ) [15] => Array ( [x] => 15 [y] => 243 ) ) x represent days and y values of a certain variable. I would like to display an array of unique days x ( last element ) and values y pragmatically. for example day 6 I have two y values but I want to display only the last one ( 243 ). Thanks for help

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  • Mathematica ListcontourPlot3D

    - by Alejandro
    I have data in the form { {x,y,z,f}...} I am using ListContourPlot3D but all I get is an empty box with dimensions -1,1 in each direction. Here is my code: ListContourPlot3D[data5, PlotRange - All, AxesLabel - {"[Beta]", "[Omega]", "Vo"}, Contours - {1500}]. These are the first 5 points of my data:( the whole set has 55 points) {{200, 20000 10^(1/3), 2000, 1226}, {200, 20000 10^(1/3), 2600, 1422}, {200, 20000 10^(1/3), 3200, 1581}, {200, 20000 10^(1/3), 3800, 1761}, {200, 20000 10^(1/3), 4400, 1872}} Dimensions[data5] returns {55,4} If I do IntegerPart[data5] it does it correctly so it must recognize the numbers in my data. I appreciate any ideas. Thank you.

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  • how to sort a multidemensional array by an inner key

    - by Derek Vance
    i have this enormous array that i am pulling from an API for BattleField Bad Company 2, and the soldier stats can be pulled as a multi dimensional array with an inner array for each soldier, however the API sormats it sorting the soldiers by name alphabetically, i want to sort them by rank (which is just another key within that soldiers array). ive been trying to figure this out for days, anyone have any ideas? (ie sort the array by $arr[players][][rank] here is a bit of the array Array ( [players] = Array ( [0] = Array ( [name] = bigjay517 [rank] = 29 [rank_name] = SECOND LIEUTENANT II [veteran] = 0 [score] = 979440 [level] = 169 [kills] = 4134 [deaths] = 3813 [time] = 292457.42 [elo] = 319.297 [form] = 1 [date_lastupdate] = 2010-03-30T14:06:20+02:00 [count_updates] = 13 [general] = Array ( [accuracy] = 0.332 [dogr] = 86 [dogt] = 166 [elo0] = 309.104 [elo1] = 230.849 [games] = 384 [goldedition] = 0 [losses] = 161 [sc_assault] = 146333 [sc_award] = 567190 [sc_bonus] = 35305 [sc_demo] = 96961 [sc_general] = 264700 [sc_objective] = 54740 [sc_recon] = 54202 [sc_squad] = 53210 [sc_support] = 70194 [sc_team] = 21215 [sc_vehicle] = 44560 [slevel] = 0 [spm] = 0 [spm0] = 0 [spm1] = 0 [srank] = 0 [sveteran] = 0 [teamkills] = 67 [udogt] = 0 [wins] = 223 )

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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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  • 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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  • Need to add an array into another array at a specified key value

    - by sologhost
    Ok, I have an array like so, but it's not guaranteed to be laid out in this order all of the time... $array = array( 'sadness' => array( 'info' => 'some info', 'info2' => 'more info', 'value' => 'value', ), 'happiness' => array( 'info' => 'some info', 'info2' => 'more info', 'value' => 'the value', ), 'peace' => array( 'info' => 'some info', 'info2' => 'more info', 'value' => 'the value', ) ); Ok, and I'd like to throw in this array right after the happiness key is defined. I can't use the key of "peace" since it must go directly after happiness, and peace might not come after happiness as this array changes. So here's what I need to add after happiness... $another_array['love'] = array( 'info' => 'some info', 'info2' => 'more info', 'value' => 'the value of love' ); So the final output after it gets inputted directly after happiness should look like this: $array = array( 'sadness' => array( 'info' => 'some info', 'info2' => 'more info', 'value' => 'value', ), 'happiness' => array( 'info' => 'some info', 'info2' => 'more info', 'value' => 'the value', ), 'love' => array( 'info' => 'some info', 'info2' => 'more info', 'value' => 'the value of love', ), 'peace' => array( 'info' => 'some info', 'info2' => 'more info', 'value' => 'the value', ) ); Can someone please give me a hand with this. Using array_shift, array_pop, or array_merge doesn't help me at all, since these go at the beginning and at the end of the array. I need to place it directly after a KEY position within $array. Thanks :)

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  • php if array key exists inside multidimentional array

    - by Richard
    how can i check if logo exists in this array called $attachements print_r is below: Array ( [logo] = /home/richar2/public_html/ioagh/images/stories/jreviews/20100510115659_1_img.gif ) when theres no logo, the array print_r's Array ( ) i tried: if (isset($attachments['logo']) ) {..} but the conditional code runs when there is no logo

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  • PHP 2D Array output all combinations

    - by stukerr
    Hi there, I've had this problem bending my mind for a while now (head cold doesn't help either!), basically I have a PHP array which looks like this example: $array[0][0] = 'apples'; $array[0][1] = 'pears'; $array[0][2] = 'oranges'; $array[1][0] = 'steve'; $array[1][1] = 'bob'; And I would like to be able to produce from this a table with every possible combination of these, but without repeating any combinations (regardless of their position), so for example this would output Array 0 Array 1 apples steve apples bob pears steve pears bob But I would like for this to be able to work with as many different arrays as possible. Many thanks!

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  • Why is numpy's einsum faster than numpy's built in functions?

    - by Ophion
    Lets start with three arrays of dtype=np.double. Timings are performed on a intel CPU using numpy 1.7.1 compiled with icc and linked to intel's mkl. A AMD cpu with numpy 1.6.1 compiled with gcc without mkl was also used to verify the timings. Please note the timings scale nearly linearly with system size and are not due to the small overhead incurred in the numpy functions if statements these difference will show up in microseconds not milliseconds: arr_1D=np.arange(500,dtype=np.double) large_arr_1D=np.arange(100000,dtype=np.double) arr_2D=np.arange(500**2,dtype=np.double).reshape(500,500) arr_3D=np.arange(500**3,dtype=np.double).reshape(500,500,500) First lets look at the np.sum function: np.all(np.sum(arr_3D)==np.einsum('ijk->',arr_3D)) True %timeit np.sum(arr_3D) 10 loops, best of 3: 142 ms per loop %timeit np.einsum('ijk->', arr_3D) 10 loops, best of 3: 70.2 ms per loop Powers: np.allclose(arr_3D*arr_3D*arr_3D,np.einsum('ijk,ijk,ijk->ijk',arr_3D,arr_3D,arr_3D)) True %timeit arr_3D*arr_3D*arr_3D 1 loops, best of 3: 1.32 s per loop %timeit np.einsum('ijk,ijk,ijk->ijk', arr_3D, arr_3D, arr_3D) 1 loops, best of 3: 694 ms per loop Outer product: np.all(np.outer(arr_1D,arr_1D)==np.einsum('i,k->ik',arr_1D,arr_1D)) True %timeit np.outer(arr_1D, arr_1D) 1000 loops, best of 3: 411 us per loop %timeit np.einsum('i,k->ik', arr_1D, arr_1D) 1000 loops, best of 3: 245 us per loop All of the above are twice as fast with np.einsum. These should be apples to apples comparisons as everything is specifically of dtype=np.double. I would expect the speed up in an operation like this: np.allclose(np.sum(arr_2D*arr_3D),np.einsum('ij,oij->',arr_2D,arr_3D)) True %timeit np.sum(arr_2D*arr_3D) 1 loops, best of 3: 813 ms per loop %timeit np.einsum('ij,oij->', arr_2D, arr_3D) 10 loops, best of 3: 85.1 ms per loop Einsum seems to be at least twice as fast for np.inner, np.outer, np.kron, and np.sum regardless of axes selection. The primary exception being np.dot as it calls DGEMM from a BLAS library. So why is np.einsum faster that other numpy functions that are equivalent? The DGEMM case for completeness: np.allclose(np.dot(arr_2D,arr_2D),np.einsum('ij,jk',arr_2D,arr_2D)) True %timeit np.einsum('ij,jk',arr_2D,arr_2D) 10 loops, best of 3: 56.1 ms per loop %timeit np.dot(arr_2D,arr_2D) 100 loops, best of 3: 5.17 ms per loop The leading theory is from @sebergs comment that np.einsum can make use of SSE2, but numpy's ufuncs will not until numpy 1.8 (see the change log). I believe this is the correct answer, but have not been able to confirm it. Some limited proof can be found by changing the dtype of input array and observing speed difference and the fact that not everyone observes the same trends in timings.

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  • 2 dimensional array

    - by ankit
    we have these arrays.... $cities = array("nagpur","kanpur","delhi","chd","Noida","mumbai","nagpur"); $names = array("munish","imteyaz","ram","shyam","ankit","Rahul","mohan"); now i want a 2 dimensional array with name of city as key and all the corresponding names as its values. <?php $cities = array("nagpur","kanpur","nagpur","delhi","kanpur"); $names = array("ankit","atul","aman","amit","manu"); foreach ($cities as $i => $value) { echo "\n"; echo $value; $city=$value; $k=0; foreach ($cities as $ii => $m) { If($city==$m) { echo$names[$ii] ; $final[$i][$k]=$names[$ii]; $arr = array($city => array($k =>$names[$ii] )); $k++; } } echo"\n<tr></tr>"; } wat i tried is this.but it doesnt work.help me

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