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  • initialize a numpy array

    - by Curious2learn
    Is there way to initialize a numpy array of a shape and add to it? I will explain what I need with a list example. If I want to create a list of objects generated in a loop, I can do: a = [] for i in range(5): a.append(i) I want to do something similar with a numpy array. I know about vstack, concatenate etc. However, it seems these require two numpy arrays as inputs. What I need is: big_array # Initially empty. This is where I don't know what to specify for i in range(5): array i of shape = (2,4) created. add to big_array The big_array should have a shape (10,4). How to do this? Thanks for your help.

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  • How do I add/remove items to a ListView in virtual mode?

    - by Eric
    If I'm using a ListView in virtual mode then, as I understand it, the list view only keeps track of a small number of items in the list. As the user scrolls it dynamically retrieves items it needs to show from the virtual list. But what if an item is added or removed from the master list? If an item is added/removed outside of the range of indexes being shown by the list view then I would assume the list view would show the added/missing items when the user scrolls to that index. Is this correct? But what if an item is added/removed from the range of indexes the user is currently viewing? How do I trigger the list view to refresh the items it is currently viewing to show the new/missing items?

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  • Why wont numpy matrix let me print its rows?

    - by uberjumper
    Okay this is probably a really dumb question, however its really starting to hurt. I have a numpy matrix, and basically i print it out row by row. However i want to make each row be formatted and separated properly. >>> arr = numpy.matrix([[x for x in range(5)] for y in range(5)]) >>> arr matrix([[0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4]]) Lets say i want to print the first row, and add a '|' between each element: >>> '|'.join(map(str, arr[0,])) '[[0 1 2 3 4]]' Err... >>> '|'.join(map(lambda x: str(x[0]), arr[0])) '[[0 1 2 3 4]]' I am really confused by this behavior why does it do this?

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  • When is ¦ not equal to ¦?

    - by Trey Jackson
    Background. I'm working with netlists, and in general, people specify different hierarchies by using /. However, it's not illegal to actually use a / as a part of an instance name. For example, X1/X2/X3/X4 might refer to instance X4 inside another instance named X1/X2/X3. Or it might refer an instance named X3/X4 inside an instance named X2 inside an instance named X1. Got it? There's really no "regular" character that cannot be used as a part of an instance name, so you resort to a non-printable one, or ... perhaps one outside of the standard 0..127 ASCII chars. I thought I'd try (decimal) 166, because for me it shows up as the pipe: ¦. So... I've got some C++ code which constructs the path name using ¦ as the hierarchical separator, so the path above looks like X1¦X2/X3¦X4. Now the GUI is written in Tcl/Tk, and to properly translate this into human readable terms I need to do something like the following: set path [getPathFromC++] ;# returns X1¦X2/X3¦X4 set humanreadable [join [split $path ¦] /] Basically, replace the ¦ with / (I could also accomplish this with [string map]). Now, the problem is, the ¦ in the string I get from C++ doesn't match the ¦ I can create in Tcl. i.e. This fails: set path [getPathFromC++] ;# returns X1¦X2/X3¦X4 string match $path [format X1%cX2/X3%cX4 166 166] Visually, the two strings look identical, but string match fails. I even tried using scan to see if I'd mixed up the bit values. But set path [getPathFromC++] ;# returns X1¦X2/X3¦X4 set path2 [format X1%cX2/X3%cX4 166 166] for {set i 0} {$i < [string length $path]} {incr i} { set p [string range $path $i $i] set p2 [string range $path2 $i $i] scan %c $p c scan %c $p2 c2 puts [list $p $c :::: $p2 $c2 equal? [string equal $c $c2]] } Produces output which looks like everything should match, except the [string equal] fails for the ¦ characters with a print line: ¦ 166 :::: ¦ 166 equal? 0 For what it's worth, the character in C++ is defined as: const char SEPARATOR = 166; Any ideas why a character outside the regular ASCII range would fail like this? When I changed the separator to (decimal) 28 (^\), things worked fine. I just don't want to get bit by a similar problem on a different platform. (I'm currently using Redhat Linux).

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  • sampling integers uniformly efficiently in python using numpy/scipy

    - by user248237
    I have a problem where depending on the result of a random coin flip, I have to sample a random starting position from a string. If the sampling of this random position is uniform over the string, I thought of two approaches to do it: one using multinomial from numpy.random, the other using the simple randint function of Python standard lib. I tested this as follows: from numpy import * from numpy.random import multinomial from random import randint import time def use_multinomial(length, num_points): probs = ones(length)/float(length) for n in range(num_points): result = multinomial(1, probs) def use_rand(length, num_points): for n in range(num_points): rand(1, length) def main(): length = 1700 num_points = 50000 t1 = time.time() use_multinomial(length, num_points) t2 = time.time() print "Multinomial took: %s seconds" %(t2 - t1) t1 = time.time() use_rand(length, num_points) t2 = time.time() print "Rand took: %s seconds" %(t2 - t1) if __name__ == '__main__': main() The output is: Multinomial took: 6.58072400093 seconds Rand took: 2.35189199448 seconds it seems like randint is faster, but it still seems very slow to me. Is there a vectorized way to get this to be much faster, using numpy or scipy? thanks.

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  • Python - List of Lists Slicing Behavior

    - by Dan Dobint
    When I define a list and try to change a single item like this: list_of_lists = [['a', 'a', 'a'], ['a', 'a', 'a'], ['a', 'a', 'a']] list_of_lists[1][1] = 'b' for row in list_of_lists: print row It works as intended. But when I try to use list comprehension to create the list: row = ['a' for range in xrange(3)] list_of_lists = [row for range in xrange(3)] list_of_lists[1][1] = 'b' for row in list_of_lists: print row It results in an entire column of items in the list being changed. Why is this? How can I achieve the desired effect with list comprehension?

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  • Recursive function causing a stack overflow

    - by dbyrne
    I am trying to write a simple sieve function to calculate prime numbers in clojure. I've seen this question about writing an efficient sieve function, but I am not to that point yet. Right now I am just trying to write a very simple (and slow) sieve. Here is what I have come up with: (defn sieve [potentials primes] (if-let [p (first potentials)] (recur (filter #(not= (mod % p) 0) potentials) (conj primes p)) primes)) For small ranges it works fine, but causes a stack overflow for large ranges: user=> (sieve (range 2 30) []) [2 3 5 7 11 13 17 19 23 29] user=> (sieve (range 2 15000) []) java.lang.StackOverflowError (NO_SOURCE_FILE:0) I thought that by using recur this would be a non-stack-consuming looping construct? What am I missing?

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  • MicroChip Sample Code setting Current to a CMPDAC, DAC threshold which expect an voltage

    - by jason hong
    Sorry, the MicroChip Forum is very slow,I prefer to use overflow site to ask questions. dsPIC33FJ06GS101/X02 and dsPIC33FJ16GSX02/X04 device Sample Code // configure comparator2 CMPCON2bits.CMPON = 1; // enable comparator CMPCON2bits.INSEL = 1; // select CMP2B input pin (RB0) CMPCON2bits.RANGE = 1; // select high range, max DAC value = Avdd/2 //CMPDACx: COMPARATOR DAC CONTROL REGISTER //CMREF<9:0>: Comparator Reference Voltage Select bits CMPDAC2 = CURR_HWLIM; // DAC threshold #define CURR_HWLIM 1023 // 1023 // 10.15 * 101A MicroChip Sample code setting CURR_HWLIM which 1023A to COMPDAC2 which expects voltage I think that's mistake.

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  • Excel VBA to check autofilter for data

    - by cav719
    I need help checking for autofiltered rows not including the header. I want it to give a message box "No records found." then exit sub or continue with copy paste if there are rows beyond the header row. I know I need an If/Else entry after the filter to check for data but I'm having trouble figuring how to check. This code is being done from a UserForm I created. Here is my script: Private Sub Searchbycompanyfield_Click() If CompanyComboBox1.Value = "" Then MsgBox "Please enter a Company to begin search." Exit Sub End If ActiveSheet.Range("$A:$H").AutoFilter Field:=1, Criteria1:=EQDataEntry.CompanyComboBox1.Value, Operator:=xlOr Cells.Select Selection.Copy Sheets("Sheet2").Select Range("A5").Select ActiveSheet.Paste Call MessageBoxYesOrNoMsgBox End Sub Any help would be greatly appreciated.

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  • Calculating the union of 2 longitudal intervals (that may wrap around 180 degrees)

    - by timpatt
    The story: I have a LatLongBounds class that represents an area on the surface of the earth by a latitudinal interval (bounded by north & south - not important to this question) and a longitudinal interval (bounded by east and west; both normalized to a range [-180, 180] - negative being a westerly direction). In order to be able to represent an area that straddles the 180 degree meridian the value of west may be set to be greater than east (eg. the range west = 170, east = -170 will straddle said meridian). In effect the longitudinal interval may wrap around at 180 degrees (or equivalently -180 degrees). My Question: Does anyone have any suggestions as to how I can calculate the union of two longitudinal intervals that may wrap around at 180 degrees. Thanks.

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  • Multiprocessing Bomb

    - by iKarampa
    I was working the following example from Doug Hellmann tutorial on multiprocessing: import multiprocessing def worker(): """worker function""" print 'Worker' return if __name__ == '__main__': jobs = [] for i in range(5): p = multiprocessing.Process(target=worker) jobs.append(p) p.start() When I tried to run it outside the if statement: import multiprocessing def worker(): """worker function""" print 'Worker' jobs = [] for i in range(5): p = multiprocessing.Process(target=worker) jobs.append(p) p.start() It started spawning processes non-stop, without any way of to terminating it. Why would that happen? Why it did not generate 5 processes and exit? Why do I need the if statement?

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  • Multiplying matrices: error: expected primary-expression before 'struct'

    - by justin
    I am trying to write a program that is supposed to multiply matrices using threads. I am supposed to fill the matrices using random numbers in a thread. I am compiling in g++ and using PTHREADS. I have also created a struct to pass the data from my command line input to the thread so it can generate the matrix of random numbers. The sizes of the two matrices are also passed in the command line as well. I keep getting: main.cpp:7: error: expected primary-expression before 'struct' my code @ line 7 =: struct a{ int Arow; int Acol; int low; int high; }; My inpust are : Sizes of two matrices ( 4 arguments) high and low ranges in which o generate the random numbers between. Complete code: [headers] using namespace std; void *matrixACreate(struct *); void *status; int main(int argc, char * argv[]) { int Arow = atoi(argv[1]); // Matrix A int Acol = atoi(argv[2]); // WxX int Brow = atoi(argv[3]); // Matrix B int Bcol = atoi(argv[4]); // XxZ, int low = atoi(argv[5]); // Range low int high = atoi(argv[6]); struct a{ int Arow; // Matrix A int Acol; // WxX int low; // Range low int high; }; pthread_t matrixAthread; //pthread_t matrixBthread; pthread_t runner; int error, retValue; if (Acol != Brow) { cout << " This matrix cannot be multiplied. FAIL" << endl; return 0; } error = pthread_create(&matrixAthread, NULL, matrixACreate, struct *a); //error = pthread_create(&matrixAthread, NULL, matrixBCreate, sendB); retValue = pthread_join(matrixAthread, &status); //retValue = pthread_join(matrixBthread, &status); return 0; } void matrixACreate(struct * a) { struct a *data = (struct a *) malloc(sizeof(struct a)); data->Arow = Arow; data->Acol = Acol; data->low = low; data->high = high; int range = ((high - low) + 1); cout << Arow << endl<< Acol << endl; }// just trying to print to see if I am in the thread

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  • Suggestion for creating custom sound recognition software to toggle audio

    - by Parrot owner
    I need to develop a program that toggles a particular audio track on or off when it recognizes a parrot scream or screech. The software would need to recognize a particular range of sounds and allow some variations in the range (as a parrot likely won't replicate its sreeches EXACTLY each time). Example: Bird screeches, no audio. Bird stops screeching for five seconds, audio track praising the bird plays. Regular chattering needs to be ignored completely, as it is not to be discouraged. I've heard of java libraries that have speech recognition with dictionaries built in, but the software would need to be taught the particular sounds that my particular parrot makes - not words or any random bird sound. In addition as I mentioned above, it would need to allow for slight variation in the sound, as the screech will likely never be 100% identical to the recorded version. What would be the best way to go about this/what language should I look into?

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  • Loop colours from variables for graphics.py [Python 3.2]

    - by user1056548
    I am creating a graphics program that draws 100 x 100 squares next to each other depending on the user-specified grid size. The user also inputs 4 colours for the squares to be coloured (e.g. if they enter red,green,blue,yellow the squares will be coloured in that order, repeating the colours). Is it possible to loop the colours from the variables the user has given? Here is what I have so far: def main(): print ("Please enter four comma seperated colours e.g.: 'red,green,blue,yellow'\n\ Allowed colours are: red, green, blue, yellow and cyan") col1, col2, col3, col4 = input("Enter your four colours: ").split(',') win = GraphWin ("Squares", 500, 500) colours = [col1, col2, col3, col4] drawSquare (win, col1, col2, col3, col4, colours) win.getMouse() win.close() def drawSquare(win, col1, col2, col3, col4, colours): for i in range (4): for j in range (len(colours)): colour = colours[j] x = 50 + (i * 50) circle = Circle (Point (x,50), 20) circle.setFill(colour) circle.draw(win) I think I should be using a list in some way, but can't work out exactly how to do it. Can anybody help?

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  • Translate imperative control flow with break-s/continue-s to haskell

    - by dorserg
    Consider the following imperative code which finds the largest palindrome among products of 3-digit numbers (yes, it's the one of the first tasks from "Project of [outstanding mathematician of 18th century]" site): curmax = 0 for i in range(999,100): for j in range(999,100): if ((i*j) < curmax): break if (pal(i*j)): curmax = i*j break print curmax As I'm learning Haskell currently, my question is, how do you translate this (and basically any imperative construct that contains something more complex than just plain iteration, e.g. breaks, continues, temporary variables and all this) to Haskell? My version is maxpal i curmax | i < 100 = curmax | otherwise = maxpal (i-1) (innerloop 999) where innerloop j | (j < 100) || (p < curmax) = curmax | pal p = p | otherwise = innerloop (j-1) where p = i*j main = print $ maxpal 999 0 but this looks like we're still in imperative uglytown. So what could you advise, what are the approaches of dealing with such cases FP-style?

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  • What's the correct way to hide/prevent access to wp-admin

    - by Jaypee
    I'm dealing with this matter since a while, I have read a ton of articles and stuff out there but I couldn't find a place that shows the RIGHT way, standard, correct, whatever you like to call it, to prevent access to my wp-admin or wp-login.php On all Wordpress sites I see (the well made ones) you will never see anything if you type thesite.com/wp-admin As I could see, one way to do this is by restricting the access to that folder by creating an .htaccess file and restrict by IP the access to the folder. Seems to be the "cleanest" way to do. What I'm not sure about it is that I have a dynamic address provided by my ISP, so on a certain time my IP will change, that will force me to also change the .htaccess to my new address, I don't see that practical. I can set a range also, but by doing that I will also authorize access to all people within that range of IPs (other clients of my ISP for example). I'm then struggling to find the best/standard way to do this. Anyone can help me? Thanks

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  • Reintegrate a branch with externals fails in SVN

    - by dnndeveloper
    What I am doing: Apply external properties to a folder in the trunk (both single file and folder external, externals are binary files) Create a branch from the trunk and update the entire project Modify a file on the branch and commit the changes, then update the entire project. Merge - "Reintegrate a branch" when I get to the last screen I click "test merge" and get this error: Error: Cannot reintegrate into mixed-revision working copy; try updating first I update the entire project and still the same error. Other observations: If I "Merge a range of revisions" everything works fine. If I remove the externals everything works fine using either "Merge a range of revisions" or "Reintegrate a branch". How do I solve this issue? I am using Subversion 1.6.6 with TortoiseSVN 1.6.6.

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  • How do I request a single random row from a force.com database in SOQL?

    - by Ollie C
    Total row-count is in the range 10k-100k rows. Can I use RAND() on force.com? Unfortunately although all the rows have a unique numeric identifier, there are many gaps, and I'd often want to select a random row from a filtered subset anyway. I suspect there's no particularly efficient way to do this, but is it possible at all? Ultimately all I want to do is to extract one row from a table (or a subset based on specific filter criteria) at random. If force.com doesn't let me select a random row, then can I query the rows to select from, and assign sequential IDs to all the rows, say 1-1,035, and then select a random number in that range locally, say 349, and then get row 349?

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  • compute mean in python for a generator

    - by nmaxwell
    Hi, I'm doing some statistics work, I have a (large) collection of random numbers to compute the mean of, I'd like to work with generators, because I just need to compute the mean, so I don't need to store the numbers. The problem is that numpy.mean breaks if you pass it a generator. I can write a simple function to do what I want, but I'm wondering if there's a proper, built-in way to do this? It would be nice if I could say "sum(values)/len(values)", but len doesn't work for genetators, and sum already consumed values. here's an example: import numpy def my_mean(values): n = 0 Sum = 0.0 try: while True: Sum += next(values) n += 1 except StopIteration: pass return float(Sum)/n X = [k for k in range(1,7)] Y = (k for k in range(1,7)) print numpy.mean(X) print my_mean(Y) these both give the same, correct, answer, buy my_mean doesn't work for lists, and numpy.mean doesn't work for generators. I really like the idea of working with generators, but details like this seem to spoil things. thanks for any help -nick

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  • Random List of millions of elements in Python Efficiently

    - by eWizardII
    Hello, I have read this answer potentially as the best way to randomize a list of strings in Python. I'm just wondering then if that's the most efficient way to do it because I have a list of about 30 million elements via the following code: import json from sets import Set from random import shuffle a = [] for i in range(0,193): json_data = open("C:/Twitter/user/user_" + str(i) + ".json") data = json.load(json_data) for j in range(0,len(data)): a.append(data[j]['su']) new = list(Set(a)) print "Cleaned length is: " + str(len(new)) ## Take Cleaned List and Randomize it for Analysis shuffle(new) If there is a more efficient way to do it, I'd greatly appreciate any advice on how to do it. Thanks,

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  • MYSQL - multiple count statments

    - by darudude
    I'm trying to do a lookup on our demographioc table to display some stats. However, since out demographic table is quit big I want to do it in one query. There are 2 fields that are important: sex, last_login I want to be able to get the total number of logins for various date ranges (<1day ago, 1-7 days ago, 7-30 days ago, etc) GROUPED BY sex I right now know how to do it for one date range. For example less than 1 day ago: SELECT sex, count(*) peeps FROM player_account_demo WHERE last_demo_update>1275868800 GROUP BY sex Which returns: sex peeps UNKNOWN 22 MALE 43 FEMALE 86 However I'd have to do this once for each range. Is there a way to get all 3 ranges in there? I'd want my end result to look something like this: sex peeps<1day peeps1-7days peeps7-30days Thanks!

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  • Switch to BigInteger if necessary

    - by fahdshariff
    I am reading a text file which contains numbers in the range [1, 10^100]. I am then performing a sequence of arithmetic operations on each number. I would like to use a BigInteger only if the number is out of the int/long range. One approach would be to count how many digits there are in the string and switch to BigInteger if there are too many. Otherwise I'd just use primitive arithmetic as it is faster. Is there a better way? Is there any reason why Java could not do this automatically i.e. switch to BigInteger if an int was too small? This way we would not have to worry about overflows.

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  • merging selected revisions from one branch on another in Mercurial

    - by Assaf Lavie
    Is it possible to merge a range of revisions from one branch to another in Mercurial? e.g. |r1 |r2 |r3 |\___ | | r5 | | r6 | | r7 | | ... | | r40 |r41 If I want to merge revisions 6 & 7, but not 5, into the main branch - is this possible? What about multiple selected revision ranges from branch A to branch B? e.g. merge 4-7, 20-25 and 30-34? (this isn't a real case, just an illustration. I'm trying to understand if hg has this revision-range merge feature that I know svn has)

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