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  • How to work with this turing machine?

    - by Lazer
    This is a screenshot of the applet LogiCell 1.0, link to which I found here. As the bottom left corner shows, this is doing sum 0+1 and the result is 01b (bottom right hand side). I am not able to link what is displayed to what the inputs ans outputs are. For example in this case - seeing the snapshot, how do you determine that the inputs are 0 and 1 and the output is 01?

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  • What pseudo-operators exist in Perl 5?

    - by Chas. Owens
    I am currently documenting all of Perl 5's operators (see the perlopref GitHub project) and I have decided to include Perl 5's pseudo-operators as well. To me, a pseudo-operator in Perl is anything that looks like an operator, but is really more than one operator or a some other piece of syntax. I have documented the four I am familiar with already: ()= the countof operator =()= the goatse/countof operator ~~ the scalar context operator }{ the Eskimo-kiss operator What other names exist for these pseudo-operators, and do you know of any pseudo-operators I have missed? =head1 Pseudo-operators There are idioms in Perl 5 that appear to be operators, but are really a combination of several operators or pieces of syntax. These pseudo-operators have the precedence of the constituent parts. =head2 ()= X =head3 Description This pseudo-operator is the list assignment operator (aka the countof operator). It is made up of two items C<()>, and C<=>. In scalar context it returns the number of items in the list X. In list context it returns an empty list. It is useful when you have something that returns a list and you want to know the number of items in that list and don't care about the list's contents. It is needed because the comma operator returns the last item in the sequence rather than the number of items in the sequence when it is placed in scalar context. It works because the assignment operator returns the number of items available to be assigned when its left hand side has list context. In the following example there are five values in the list being assigned to the list C<($x, $y, $z)>, so C<$count> is assigned C<5>. my $count = my ($x, $y, $z) = qw/a b c d e/; The empty list (the C<()> part of the pseudo-operator) triggers this behavior. =head3 Example sub f { return qw/a b c d e/ } my $count = ()= f(); #$count is now 5 my $string = "cat cat dog cat"; my $cats = ()= $string =~ /cat/g; #$cats is now 3 print scalar( ()= f() ), "\n"; #prints "5\n" =head3 See also L</X = Y> and L</X =()= Y> =head2 X =()= Y This pseudo-operator is often called the goatse operator for reasons better left unexamined; it is also called the list assignment or countof operator. It is made up of three items C<=>, C<()>, and C<=>. When X is a scalar variable, the number of items in the list Y is returned. If X is an array or a hash it it returns an empty list. It is useful when you have something that returns a list and you want to know the number of items in that list and don't care about the list's contents. It is needed because the comma operator returns the last item in the sequence rather than the number of items in the sequence when it is placed in scalar context. It works because the assignment operator returns the number of items available to be assigned when its left hand side has list context. In the following example there are five values in the list being assigned to the list C<($x, $y, $z)>, so C<$count> is assigned C<5>. my $count = my ($x, $y, $z) = qw/a b c d e/; The empty list (the C<()> part of the pseudo-operator) triggers this behavior. =head3 Example sub f { return qw/a b c d e/ } my $count =()= f(); #$count is now 5 my $string = "cat cat dog cat"; my $cats =()= $string =~ /cat/g; #$cats is now 3 =head3 See also L</=> and L</()=> =head2 ~~X =head3 Description This pseudo-operator is named the scalar context operator. It is made up of two bitwise negation operators. It provides scalar context to the expression X. It works because the first bitwise negation operator provides scalar context to X and performs a bitwise negation of the result; since the result of two bitwise negations is the original item, the value of the original expression is preserved. With the addition of the Smart match operator, this pseudo-operator is even more confusing. The C<scalar> function is much easier to understand and you are encouraged to use it instead. =head3 Example my @a = qw/a b c d/; print ~~@a, "\n"; #prints 4 =head3 See also L</~X>, L</X ~~ Y>, and L<perlfunc/scalar> =head2 X }{ Y =head3 Description This pseudo-operator is called the Eskimo-kiss operator because it looks like two faces touching noses. It is made up of an closing brace and an opening brace. It is used when using C<perl> as a command-line program with the C<-n> or C<-p> options. It has the effect of running X inside of the loop created by C<-n> or C<-p> and running Y at the end of the program. It works because the closing brace closes the loop created by C<-n> or C<-p> and the opening brace creates a new bare block that is closed by the loop's original ending. You can see this behavior by using the L<B::Deparse> module. Here is the command C<perl -ne 'print $_;'> deparsed: LINE: while (defined($_ = <ARGV>)) { print $_; } Notice how the original code was wrapped with the C<while> loop. Here is the deparsing of C<perl -ne '$count++ if /foo/; }{ print "$count\n"'>: LINE: while (defined($_ = <ARGV>)) { ++$count if /foo/; } { print "$count\n"; } Notice how the C<while> loop is closed by the closing brace we added and the opening brace starts a new bare block that is closed by the closing brace that was originally intended to close the C<while> loop. =head3 Example # count unique lines in the file FOO perl -nle '$seen{$_}++ }{ print "$_ => $seen{$_}" for keys %seen' FOO # sum all of the lines until the user types control-d perl -nle '$sum += $_ }{ print $sum' =head3 See also L<perlrun> and L<perlsyn> =cut

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  • How to evaluate query by DBMS?

    - by Kevinniceguy
    Sorry...I mean what question will be for this query? SELECT SUM(price) FROM Room r, Hotel h WHERE r.hotelNo = h.hotelNo and hotelName = 'Paris Hilton' and roomNo NOT IN (SELECT roomNo FROM Booking b, Hotel h WHERE (dateFrom <= CURRENT_DATE AND dateTo >= CURRENT_DATE) AND b.hotelNo = h.hotelNo AND hotelName = 'Paris Hilton');

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  • Calculating multiple column average in SQLite3

    - by Benjamin Oakes
    I need to average some values in a row-wise fashion, rather than a column-wise fashion. (If I were doing a column-wise average, I could just use avg()). My specific application of this requires me ignore NULLs in averaging. It's pretty straightforward logic, but seems awfully difficult to do in SQL. Is there an elegant way of doing my calculation? I'm using SQLite3, for what it's worth. Details If you need more details, here's an illustration: I have a a table with a survey: | q1 | q2 | q3 | ... | q144 | |----|-------|-------|-----|------| | 1 | 3 | 7 | ... | 2 | | 4 | 2 | NULL | ... | 1 | | 5 | NULL | 2 | ... | 3 | (Those are just some example values and simple column names. The valid values are 1 through 7 and NULL.) I need to calculate some averages like so: q7 + q33 + q38 + q40 + ... + q119 / 11 as domain_score_1 q10 + q11 + q34 + q35 + ... + q140 / 13 as domain_score_2 ... q2 + q5 + q13 + q25 + ... + q122 / 12 as domain_score_14 ...but i need to pull out the nulls and average based on the non-nulls. So, for domain_score_1 (which has 11 items), I would need to do: Input: 3, 5, NULL, 7, 2, NULL, 3, 1, 5, NULL, 1 (3 + 5 + 7 + 2 + 3 + 1 + 5 + 1) / (11 - 3) 27 / 8 3.375 A simple algorithm I'm considering is: Input: 3, 5, NULL, 7, 2, NULL, 3, 1, 5, NULL, 1 Coalesce each value to 0 if NULL: 3, 5, 0, 7, 2, 0, 3, 1, 5, 0, 1 Sum: 27 Get the number of non-zeros by converting values 0 to 1 and sum: 3, 5, 0, 7, 2, 0, 3, 1, 5, 0, 1 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1 8 Divide those two numbers 27 / 8 3.375 But that seems like a lot more programming than this should take. Is there an elegant way of doing this that I'm not aware of? Update: Unless I'm misunderstanding something, avg() won't work for this. Example of what I would want to do: select avg(q7, q33, q38, ..., q119) from survey; Output: SQL error near line 3: wrong number of arguments to function avg()

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  • What is the best way to document a system metaphor?

    - by SDReyes
    A metaphor help us to communicate with our project stakeholders, using a shared set of concepts and analogies. we develop them all the time, in one way or another. even the XP- programming highly recommend to get it defined since project start. How do you write such thing down in a document (specially if it already exists)? maybe a dictionary-like approach? UPDATE: perhaps a thesaurus would do it better (synonyms sum).

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  • Dijkstra shortest path algorithm with edge cost.

    - by Svisstack
    Hello, I have a directed, positive weighted graph. Each edge have a cost of use. I have only A money, i want to calculate shortest paths with dijkstra algorithm, but sum of edges costs on route must be less or equal to A. I want to do this with most smallest Dijstra modification (if I can do it with small modification of Dijkstra). Anyone can help me with this?

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  • Saving integers as Strings in MIPS

    - by Krewie
    Hello , i was just wondering, is there any way in MIPS to store a summation of numbers as a string and later read them byte by byte, for example: the sum 657 - sw into a .ascii directive - later lb on the first index to get 6 (in ascii code) same with 5 and so on Is this possible ? //Thx in advance

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  • how to evaluate query by DMBS?

    - by Kevinniceguy
    How do we evaluate the below database query by DBMS? the query is something like : SELECT SUM(price) FROM Room r, Hotel h WHERE r.hotelNo = h.hotelNo and hotelName = 'Paris Hilton' and roomNo NOT IN (SELECT roomNo FROM Booking b, Hotel h WHERE (dateFrom <= CURRENT_DATE AND dateTo = CURRENT_DATE) AND b.hotelNo = h.hotelNo AND hotelName = 'Paris Hilton');

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  • Count number of arguments to Excel formula in VBA

    - by Abiel
    I need to use VBA to determine the number of arguments passed to an Excel formula. For instance, suppose a cell contains the formula =MyFunc($A$1, "xyz", SUM(1,2,COUNT(C1:C12)), IF(B12,1,0)). Then the counter function should return 4. Does VBA contain any built-in functions for this, or does someone have an example of a regular expression that could calculate this?

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  • how to locate path (mobile) c#

    - by tike
    hi, i was trying to locate specific path for a picture (that i want to include) in mobile application (web server). and in terms of doing that i did this.. image src= \\program files\myprogram\a.jpg is that how it works is mobile device? to sum up, i was stuck being unable to display picture from specific path. any help appreciated thanks

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  • SQLSTATE[HY093]: Invalid parameter number: mixed named and positional parameters

    - by Gremo
    Weird error and this is driving me crazy all the day. To me it seems a bug because there are no positional parameters in my query. Here is the method: public function getAll(User $user, DateTime $start = null, DateTime $end = null) { $params = array('user_id' => $user->getId()); $rsm = new \Doctrine\ORM\Query\ResultSetMapping(); // Result set mapping $rsm->addScalarResult('subtype', 'subtype'); $rsm->addScalarResult('count', 'count'); $sms_sql = "SELECT CONCAT('sms_', IF(is_auto = 0, 'user' , 'auto')) AS subtype, " . "SUM(messages_count * (customers_count + recipients_count)) AS count " . "FROM outgoing_message AS m INNER JOIN small_text_message AS s ON " . "m.id = s.id WHERE status <> 'pending' AND user_id = :user_id"; $news_sql = "SELECT CONCAT('news_', IF(is_auto = 0, 'user' , 'auto')) AS subtype, " . "SUM(customers_count + recipients_count) AS count " . "FROM outgoing_message AS m JOIN newsletter AS n ON m.id = n.id " . "WHERE status <> 'pending' AND user_id = :user_id"; if($start) : $sms_sql .= " AND sent_at >= :start"; $news_sql .= " AND sent_at >= :start"; $params['start'] = $start->format('Y-m-d'); endif; $sms_sql .= ' GROUP BY type, is_auto'; $news_sql .= ' GROUP BY type, is_auto'; return $this->_em->createNativeQuery("$sms_sql UNION ALL $news_sql", $rsm) >setParameters($params)->getResult(); } And this throws the exception: SQLSTATE[HY093]: Invalid parameter number: mixed named and positional parameters Array $arams is OK and so generated SQL: var_dump($params); array (size=2) 'user_id' => int 1 'start' => string '2012-01-01' (length=10) Strangest thing is that it works with "$sms_sql" only! Any help would make my day, thanks. Update Found another strange thing. If i change only the name (to start_date instead of start): if($start) : $sms_sql .= " AND sent_at >= :start_date"; $news_sql .= " AND sent_at >= :start_date"; $params['start_date'] = $start->format('Y-m-d'); endif; What happens is that Doctrine/PDO says: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'sent1rt_date' in 'where clause' ... as string 1rt was added in the middle of the column name! Crazy...

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  • Autocorrelation returns random results with mic input (using a high pass filter)

    - by Niall
    Hello, Sorry to ask a similar question to the one i asked before (FFT Problem (Returns random results)), but i've looked up pitch detection and autocorrelation and have found some code for pitch detection using autocorrelation. Im trying to do pitch detection of a users singing. Problem is, it keeps returning random results. I've got some code from http://code.google.com/p/yaalp/ which i've converted to C++ and modified (below). My sample rate is 2048, and data size is 1024. I'm detecting pitch of both a sine wave and mic input. The frequency of the sine wave is 726.0, and its detecting it to be 722.950820 (which im ok with), but its detecting the pitch of the mic as a random number from around 100 to around 1050. I'm now using a High pass filter to remove the DC offset, but it's not working. Am i doing it right, and if so, what else can i do to fix it? Any help would be greatly appreciated! double* doHighPassFilter(short *buffer) { // Do FFT: int bufferLength = 1024; float *real = malloc(bufferLength*sizeof(float)); float *real2 = malloc(bufferLength*sizeof(float)); for(int x=0;x<bufferLength;x++) { real[x] = buffer[x]; } fft(real, bufferLength); for(int x=0;x<bufferLength;x+=2) { real2[x] = real[x]; } for (int i=0; i < 30; i++) //Set freqs lower than 30hz to zero to attenuate the low frequencies real2[i] = 0; // Do inverse FFT: inversefft(real2,bufferLength); double* real3 = (double*)real2; return real3; } double DetectPitch(short* data) { int sampleRate = 2048; //Create sine wave double *buffer = malloc(1024*sizeof(short)); double amplitude = 0.25 * 32768; //0.25 * max length of short double frequency = 726.0; for (int n = 0; n < 1024; n++) { buffer[n] = (short)(amplitude * sin((2 * 3.14159265 * n * frequency) / sampleRate)); } doHighPassFilter(data); printf("Pitch from sine wave: %f\n",detectPitchCalculation(buffer, 50.0, 1000.0, 1, 1)); printf("Pitch from mic: %f\n",detectPitchCalculation(data, 50.0, 1000.0, 1, 1)); return 0; } // These work by shifting the signal until it seems to correlate with itself. // In other words if the signal looks very similar to (signal shifted 200 data) than the fundamental period is probably 200 data // Note that the algorithm only works well when there's only one prominent fundamental. // This could be optimized by looking at the rate of change to determine a maximum without testing all periods. double detectPitchCalculation(double* data, double minHz, double maxHz, int nCandidates, int nResolution) { //-------------------------1-------------------------// // note that higher frequency means lower period int nLowPeriodInSamples = hzToPeriodInSamples(maxHz, 2048); int nHiPeriodInSamples = hzToPeriodInSamples(minHz, 2048); if (nHiPeriodInSamples <= nLowPeriodInSamples) printf("Bad range for pitch detection."); if (1024 < nHiPeriodInSamples) printf("Not enough data."); double *results = new double[nHiPeriodInSamples - nLowPeriodInSamples]; //-------------------------2-------------------------// for (int period = nLowPeriodInSamples; period < nHiPeriodInSamples; period += nResolution) { double sum = 0; // for each sample, find correlation. (If they are far apart, small) for (int i = 0; i < 1024 - period; i++) sum += data[i] * data[i + period]; double mean = sum / 1024.0; results[period - nLowPeriodInSamples] = mean; } //-------------------------3-------------------------// // find the best indices int *bestIndices = findBestCandidates(nCandidates, results, nHiPeriodInSamples - nLowPeriodInSamples - 1); //note findBestCandidates modifies parameter // convert back to Hz double *res = new double[nCandidates]; for (int i=0; i < nCandidates;i++) res[i] = periodInSamplesToHz(bestIndices[i]+nLowPeriodInSamples, 2048); double pitch2 = res[0]; free(res); free(results); return pitch2; } /// Finds n "best" values from an array. Returns the indices of the best parts. /// (One way to do this would be to sort the array, but that could take too long. /// Warning: Changes the contents of the array!!! Do not use result array afterwards. int* findBestCandidates(int n, double* inputs,int length) { //int length = inputs.Length; if (length < n) printf("Length of inputs is not long enough."); int *res = new int[n]; double minValue = 0; for (int c = 0; c < n; c++) { // find the highest. double fBestValue = minValue; int nBestIndex = -1; for (int i = 0; i < length; i++) { if (inputs[i] > fBestValue) { nBestIndex = i; fBestValue = inputs[i]; } } // record this highest value res[c] = nBestIndex; // now blank out that index. if(nBestIndex!=-1) inputs[nBestIndex] = minValue; } return res; } int hzToPeriodInSamples(double hz, int sampleRate) { return (int)(1 / (hz / (double)sampleRate)); } double periodInSamplesToHz(int period, int sampleRate) { return 1 / (period / (double)sampleRate); } Thanks, Niall. Edit: Changed the code to implement a high pass filter with a cutoff of 30hz (from What Are High-Pass and Low-Pass Filters?, can anyone tell me how to convert the low-pass filter using convolution to a high-pass one?) but it's still returning random results. Plugging it into a VST host and using VST plugins to compare spectrums isn't an option to me unfortunately.

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  • replace selfjoin with analytic functions

    - by edwards
    Hi Any ideas how i go about replacing the following self join using analytics SELECT t1.col1 col1, t1.col2 col2, SUM((extract(hour FROM (t1.times_stamp - t2.times_stamp)) * 3600 + extract(minute FROM ( t1.times_stamp - t2.times_stamp)) * 60 + extract(second FROM ( t1.times_stamp - t2.times_stamp)) ) ) div, COUNT(*) tot_count FROM tab1 t1, tab1 t2 WHERE t2.col1 = t1.col1 AND t2.col2 = t1.col2 AND t2.col3 = t1.sequence_num AND t2.times_stamp < t1.times_stamp AND t2.col4 = 3 AND t1.col4 = 4 AND t2.col5 NOT IN(103,123) AND t1.col5 != 549 GROUP BY t1.col1, t1.col2

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  • Derivative of a Higher-Order Function

    - by Claudiu
    This is in the context of Automatic Differentiation - what would such a system do with a function like map, or filter - or even one of the SKI Combinators? Example: I have the following function: def func(x): return sum(map(lambda a: a**x, range(20))) What would its derivative be? What will an AD system yield as a result? (This function is well-defined on real-number inputs).

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  • sql rounding value

    - by fishhead
    hello, I have been sucsessful at rounding my value to one decimal point but I would like to trim off the multitude oz trailing zeros. ROUND(SUM(Duration ),1) ends up giving me 16.9000000000000000 how do I trim all those trailing zeros. thanks mssql

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  • Is it possible to use calculated fields in aggregated fields?

    - by Jørn E. Angeltveit
    Is it possible to use a calculated field in an aggregated field in a TClientDataSet? object cdsOrders: TClientDataSet AggregatesActive = True object cdsOrdersPrice : TIntegerField FieldName = 'Price' end object cdsOrdersCount: : TIntegerField FieldName = 'Count' end object cdsOrdersCalcTotal: TIntegerField FieldKind = fkInternalCalc FieldName = 'CalcTotal' Calculated = True end object cdsOrdersAggGrandTotal: TAggregateField FieldName = 'AggGrandTotal' Active = True Expression = 'SUM(CalcTotal)' end end

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  • Vector addition of lists

    - by ntimes
    If I had a N lists each of length M, how could I write a nice clean function to return a single list of length M, where each element is the sum of the corresponding elements in the N lists? (starting to learn lisp - go easy!)

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  • Good Hash Function for Strings

    - by Leif Andersen
    I'm trying to think up a good hash function for strings. And I was thinking it might be a good idea to sum up the unicode values for the first five characters in the string (assuming it has five, otherwise stop where it ends). Would that be a good idea, or is it a bad one? I am doing this in Java, but I wouldn't imagine that would make much of a difference.

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