Search Results

Search found 9047 results on 362 pages for 'double math'.

Page 65/362 | < Previous Page | 61 62 63 64 65 66 67 68 69 70 71 72  | Next Page >

• Solving simultaneous equations

  - by Milo

  Here is my problem: Given x, y, z and ratio where z is known and ratio is known and is a float representing a relative value, I need to find x and y. I know that: x / y == ratio y - x == z What I'm trying to do is make my own scroll pane and I'm figuring out the scrollbar parameters. So for example, If the scrollbar must be able to scroll 100 values (z) and the thumb must consume 80% of the bar (ratio = 0.8) then x would be 400 and y would be 500. Thanks

  Read the article

• adding up value of array and getting the average

  - by sea_1987

  I have an array that looks similar to this, [4] => Common_Model Object ( [id] => 4 [name] => [date_created] => [last_updated] => [user_id_updated] => [_table] => [_aliases] => Array ( [id] => 4 [name] => [date_created] => [date_updated] => [user_id_updated] => [rating] => 3 [recipe_id] => 5 ) [_nonDBAliases] => Array ( ) [_default] => Array ( ) [_related] => Array ( ) [_enums] => [_alsoDelete] => Array ( ) [_readOnly] => Array ( [0] => date_updated ) [_valArgs] => Array ( ) [_valArgsHash] => Array ( [default] => Array ( ) ) [_valAliases] => Array ( ) [_extraData] => Array ( ) [_inputs] => Array ( ) [_tableName] => jm_ratings [_tablePrefix] => [_niceDateUpdated] => 1st Jan 70 [_niceDateCreated] => 1st Jan 70 [_fetchAdminData] => [_mCache] => [_assets] => Array ( ) ) [3] => Common_Model Object ( [id] => 3 [name] => [date_created] => [last_updated] => [user_id_updated] => [_table] => [_aliases] => Array ( [id] => 3 [name] => [date_created] => [date_updated] => [user_id_updated] => [rating] => 1 [recipe_id] => 5 ) [_nonDBAliases] => Array ( ) [_default] => Array ( ) [_related] => Array ( ) [_enums] => [_alsoDelete] => Array ( ) [_readOnly] => Array ( [0] => date_updated ) [_valArgs] => Array ( ) [_valArgsHash] => Array ( [default] => Array ( ) ) [_valAliases] => Array ( ) [_extraData] => Array ( ) [_inputs] => Array ( ) [_tableName] => jm_ratings [_tablePrefix] => [_niceDateUpdated] => 1st Jan 70 [_niceDateCreated] => 1st Jan 70 [_fetchAdminData] => [_mCache] => [_assets] => Array ( ) ) [2] => Common_Model Object ( [id] => 2 [name] => [date_created] => [last_updated] => [user_id_updated] => [_table] => [_aliases] => Array ( [id] => 2 [name] => [date_created] => [date_updated] => [user_id_updated] => [rating] => 1 [recipe_id] => 5 ) [_nonDBAliases] => Array ( ) [_default] => Array ( ) [_related] => Array ( ) [_enums] => [_alsoDelete] => Array ( ) [_readOnly] => Array ( [0] => date_updated ) [_valArgs] => Array ( ) [_valArgsHash] => Array ( [default] => Array ( ) ) [_valAliases] => Array ( ) [_extraData] => Array ( ) [_inputs] => Array ( ) [_tableName] => jm_ratings [_tablePrefix] => [_niceDateUpdated] => 1st Jan 70 [_niceDateCreated] => 1st Jan 70 [_fetchAdminData] => [_mCache] => [_assets] => Array ( ) ) I wanting to add up the [rating] and get the mean average. But I dont know how do this with PHP, my attempt looks like this, <?php foreach ($rt as $rating) { $total = $rating->rating + $rating->rating } $total / count($rt); ?>

  Read the article

• Python - How to find a correlation between two vectors ?

  - by psihodelia

  Given two vectors X and Y I have to find their correlation, i.e. their linear dependence/independence. Both vectors have equal dimension. A resulted answer should be a floating point number from [-1.0 .. 1.0]. Example: X=[-1, 2, 0] Y=[ 4, 2, -0.3] Find y=cor(X,Y) such that y belongs to [-1.0 .. 1.0]. It should be a simple construction involving a list-comprehension. No external library is allowed. UPDATE: ok, if dot product is enough, then here is my solution: nX = 1/(sum([x*x for x in X]) ** 0.5) nY = 1/(sum([y*y for y in Y]) ** 0.5) cor = sum([(x*nX)*(y*nY) for x,y in zip(X,Y) ]) right?

  Read the article

• Generate RTT values

  - by Jean Gauthier

  Hi all, I'm writing a Java applet where I should be able to simulate a connection between two hosts. Hence I have to generate packet round-trip times at random. These RTTs can go from ~0 to infinity, but are typically oscillating around some average value (i.e. an extremely large or small value is very improbable but possible). I was wondering if anyone had an idea of how I could do this? Thanks in advance

  Read the article

• Ruby BigDecimal sanity check (floating point newb)

  - by Andy

  Hello, Hoping to get some feedback from someone more experienced here. I haven't dealt with the dreaded floating-point calculation before... Is my understanding correct that with Ruby BigDecimal types (even with varying precision and scale lengths) should calculate accurately or should I anticipate floating point shenanigans? All my values within a Rails application are BigDecimal type and I'm seeing some errors (they do have different decimal lengths), hoping it's just my methods and not my object types... Thanks!

  Read the article

• Express any number as the sum of 4 prime numbers [Doubts]

  - by WarDoGG

  I was give a problem to express any number as sum of 4 prime numbers. Conditions: Not allowed to use any kind of database. Maximum execution time : 3 seconds Numbers only till 100,000 If the splitting is NOT possible, then return -1 What i did : using the sieve of eratosthenes, i calculated all prime numbers till the specified number. looked up a concept called goldbach conjecture which expresses an even number as the summation of 2 primes. However, i am stuck beyond that. Can anyone help me on this one as to what approach u might take ? The sieve of eratosthenes is taking 2 seconds to count primes till 100,000 :(((

  Read the article

• Looking for C# framework for plotting scientific data: 2d/3d ...

  - by Ivan

  I need to visualize some scientific calculations. I generally prefer reusing code if there is already a good available instead of inventing wheels each time, that's why I am asking. I need a C# code to draw charts (just outputting a bitmap is ok) of 2d (y=f(x)) and 3d (z=f(x,y)) digital data sets (where any axis can be float, int or datetime), sometimes combined. If I go here and click 3D in the navigation bar on the left, there I can see what I need. But the cheapest version costs $759 there, looks scary for a hobby project of an east-european student :-(

  Read the article

• Is there any valid reason radians are used as the inputs to trig function in many modern languages?

  - by johnmortal

  Is there any pressing reason trig functions should use radian inputs in modern programming languages? As far as I know radians are typically ugly to deal with except in three cases: (1) You want to compute an arc length and you know the angle of the arc and (2) You need to do symbolic calculus with trig functions (3) certain infinite series expansion look prettier if the input is in radians. None of these scenarios seem like a worthy justification for every programming language I am familiar with using radian inputs for Sin, Cos, Tangent, etc... The third one sounds good because it might mean one gets faster computations using radians (very slightly faster- the cost of one additional floating point multiplication ) , but I am dubious even of that because most commonly the developer had to take an extra step to put the angle in radians in the first place. The other two are ridiculous justifications for all the added obscurity.

  Read the article

• Need some help understanding this problem

  - by Legend

  I was wondering if someone could help me understand this problem. I prepared a small diagram because it is much easier to explain it visually. Problem I am trying to solve: 1. Constructing the dependency graph Given the connectivity of the graph and a metric that determines how well a node depends on the other, order the dependencies. For instance, I could put in a few rules saying that node 3 depends on node 4 node 2 depends on node 3 node 3 depends on node 5 But because the final rule is not "valuable" (again based on the same metric), I will not add the rule to my system. 2. Execute the request order Once I built a dependency graph, execute the list in an order that maximizes the final connectivity. First and foremost, I am wondering if I constructed the problem correctly and if I should be aware of any corner cases. Secondly, is there a closely related algorithm that I can look at? Currently, I am thinking of something like Feedback Arc Set or the Secretary Problem but I am a little confused at the moment. Any suggestions? PS: I am a little confused about the problem myself so please don't flame on me for that. If any clarifications are needed, I will try to update the question.

  Read the article

• How would I find all sets of N single-digit, non-repeating numbers that add up to a given sum in PHP

  - by TerranRich

  Let's say I want to find all sets of 5 single-digit, non-repeating numbers that add up to 30... I'd end up with [9,8,7,5,1], [9,8,7,4,2], [9,8,6,4,3], [9,8,6,5,2], [9,7,6,5,3], and [8,7,6,5,4]. Each of those sets contains 5 non-repeating digits that add up to 30, the given sum. Any help would be greatly appreciated. Even just a starting point for me to use would be awesome. I came up with one method, which seems like a long way of going about it: get all unique 5-digit numbers (12345, 12346, 12347, etc.), add up the digits, and see if it equals the given sum (e.g. 30). If it does, add it to the list of possible matching sets. I'm doing this for a personal project, which will help me in solving Kakuro puzzles without actually solving the whole thing at once. Yeah, it may be cheating, but it's... it's not THAT bad... :P

  Read the article

• Base 62 conversion in Python

  - by mikl

  How would you convert an integer to base 62 (like hexadecimal, but with these digits: '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'). I have been trying to find a good Python library for it, but they all seems to be occupied with converting strings. The Python base64 module only accepts strings and turns a single digit into four characters. I was looking for something akin to what URL shorteners use.

  Read the article

• Learning Basic Mathematics

  - by NeedsToKnow

  I'm going to just come out and say it. I'm 20 and can't do maths. Two years ago I passed the end-of-high-school mathematics exam (but not at school), and did pretty well. Since then, I haven't done a scrap of mathematics. I wondered just how bad I had gotten, so I was looking at some simple algebra problems. You know, the kind you learn halfway through highschool. 5(-3x - 2) - (x - 3) = -4(4x + 5) + 13 Couldn't do them. I've got half a year left until I start a Computer Science undergraduate degree. I love designing and creating programs, and I remember I loved mathematics back when I did it. Basically, I've had a pretty bad education, but I want to be knowledgable in these areas. I was thinking of buying some high school textbooks and reading them, but I'm not sure this is the right way to go. I need to start off at some basic level and work towards a greater understanding. My question is: What should I study, how should I study, and what books can you recommend? Thanks!

  Read the article

• approximating log10[x^k0 + k1]

  - by Yale Zhang

  Greetings. I'm trying to approximate the function Log10[x^k0 + k1], where .21 < k0 < 21, 0 < k1 < ~2000, and x is integer < 2^14. k0 & k1 are constant. For practical purposes, you can assume k0 = 2.12, k1 = 2660. The desired accuracy is 5*10^-4 relative error. This function is virtually identical to Log[x], except near 0, where it differs a lot. I already have came up with a SIMD implementation that is ~1.15x faster than a simple lookup table, but would like to improve it if possible, which I think is very hard due to lack of efficient instructions. My SIMD implementation uses 16bit fixed point arithmetic to evaluate a 3rd degree polynomial (I use least squares fit). The polynomial uses different coefficients for different input ranges. There are 8 ranges, and range i spans (64)2^i to (64)2^(i + 1). The rational behind this is the derivatives of Log[x] drop rapidly with x, meaning a polynomial will fit it more accurately since polynomials are an exact fit for functions that have a derivative of 0 beyond a certain order. SIMD table lookups are done very efficiently with a single _mm_shuffle_epi8(). I use SSE's float to int conversion to get the exponent and significand used for the fixed point approximation. I also software pipelined the loop to get ~1.25x speedup, so further code optimizations are probably unlikely. What I'm asking is if there's a more efficient approximation at a higher level? For example: Can this function be decomposed into functions with a limited domain like log2((2^x) * significand) = x + log2(significand) hence eliminating the need to deal with different ranges (table lookups). The main problem I think is adding the k1 term kills all those nice log properties that we know and love, making it not possible. Or is it? Iterative method? don't think so because the Newton method for log[x] is already a complicated expression Exploiting locality of neighboring pixels? - if the range of the 8 inputs fall in the same approximation range, then I can look up a single coefficient, instead of looking up separate coefficients for each element. Thus, I can use this as a fast common case, and use a slower, general code path when it isn't. But for my data, the range needs to be ~2000 before this property hold 70% of the time, which doesn't seem to make this method competitive. Please, give me some opinion, especially if you're an applied mathematician, even if you say it can't be done. Thanks.

  Read the article

• How do I find the largest factor of an integer in mysql

  - by Bill H

  I am trying to write a select query that will dynamically determine the minimum number of items that can be packaged together. I am having trouble with one part of the query. ... CASE WHEN (pid.product_id) THEN 1 WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 11 = 0)) THEN CEILING(p.inner_pack / 11) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 7 = 0)) THEN CEILING(p.inner_pack / 7) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 6 = 0)) THEN CEILING(p.inner_pack / 6) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 5 = 0)) THEN CEILING(p.inner_pack / 5) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 4 = 0)) THEN CEILING(p.inner_pack / 4) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 3 = 0)) THEN CEILING(p.inner_pack / 3) WHEN ((p.case_pack = p.inner_pack) AND (p.inner_pack % 2 = 0)) THEN CEILING(p.inner_pack / 2) ELSE p.inner_pack END AS min_pack ... What I want to do is find the largest factorial of an integer (p.inner_pack) that is under 12. Is there a better way to do this in mysql?

  Read the article

• Why can't decimal numbers be represented exactly in binary?

  - by Barry Brown

  There have been several questions posted to SO about floating-point representation. For example, the decimal number 0.1 doesn't have an exact binary representation, so it's dangerous to use the == operator to compare it to another floating-point number. I understand the principles behind floating-point representation. What I don't understand is why, from a mathematical perspective, are the numbers to the right of the decimal point any more "special" that the ones to the left? For example, the number 61.0 has an exact binary representation because the integral portion of any number is always exact. But the number 6.10 is not exact. All I did was move the decimal one place and suddenly I've gone from Exactopia to Inexactville. Mathematically, there should be no intrinsic difference between the two numbers -- they're just numbers. By contrast, if I move the decimal one place in the other direction to produce the number 610, I'm still in Exactopia. I can keep going in that direction (6100, 610000000, 610000000000000) and they're still exact, exact, exact. But as soon as the decimal crosses some threshold, the numbers are no longer exact. What's going on? Edit: to clarify, I want to stay away from discussion about industry-standard representations, such as IEEE, and stick with what I believe is the mathematically "pure" way. In base 10, the positional values are: ... 1000 100 10 1 1/10 1/100 ... In binary, they would be: ... 8 4 2 1 1/2 1/4 1/8 ... There are also no arbitrary limits placed on these numbers. The positions increase indefinitely to the left and to the right.

  Read the article

• What is SVD(singular value decomposition)

  - by shiva

  How does it actually reduce noise..can you suggest some nice tutorials?

  Read the article

• Find the sum of consecutive whole numbers w/o using loop in JavaScript

  - by Zlatev

  I'm looking for a method to do calculations like: function sumIntegerUpTo(number) { return 1+2+3+...+number; } If you pass number as 5 function should return the sum of 1+2+3+4+5. I'm wondering if it's possible to do without loops.

  Read the article

• The bigger value in a matrix row

  - by marionmaiden

  How can I get the 2 biggers numbers of a matrix row? If the matrix have a bigger number in other row, it can't be shown. For example, let's suppose I have the following matrix int mat[][] ={{1,2,3}{4,5,6}{7,8,9}}; if I search the 2 biggers numbers from the row 0, it should return me 1 and 2.

  Read the article

• Is there a good (flexible, feature-rich, KISS, modern) free C# framework for drawing charts (just ou

  - by Ivan

  I need to visualize some scientific calculations. I generally prefer reusing code if there is already a good available instead of inventing wheels each time, that's why I am asking. I need a C# code to draw charts (just outputting a bitmap is ok) of 2d (y=f(x)) and 3d (z=f(x,y)) digital data sets (where any axis can be float, int or datetime), sometimes combined.

  Read the article

• Looking for interesing formula

  - by Thinker

  I'm creating a game, where players can make an alloy. To make it less predictable, and more interesting, I thought that durability and hardness of an alloy can't be calculated by simple formula, because it will be extremely easy to find extrema, where alloy have best statistics. So the questions is, is there any formula for a function, where extrema can be found only by investigating all points? Input values will be in percents: 0.0%-100.0%. I think, it should look like this: half sound wave

  Read the article

• question about complex values in java

  - by davit-datuashvili

  We know that the general form of complex numbers is like this: z=a+i*b, where i is sqrt(-1). I have a question about how to express this in Java ?

  Read the article

• Moving a Ball on iPhone

  - by Chandan Shetty SP

  I am using below formula to move the ball circular, where accelX and accelY are the values from accelerometer, it is working fine. But the problem in this code is mRadius(I fixed its value to 50), i need to change mRadius according to accelerometer values and also i need bouncing effect when it touches other circles please send your answers ASAP... I am waiting. float degrees = -atan2(accelX, accelY) * 180 / 3.14159; int x = cCentrePoint.x + mRadius * cos(degreesToRadians(degrees)); int y = cCentrePoint.y + mRadius * sin(degreesToRadians(degrees)); Here is the snap of the game i want to develop. http://iphront.com/wp-content/uploads/2009/12/bdece528ea334033.jpg.jpg

  Read the article

• Position elements without overlap

  - by eWolf

  I have a number of rectangular elements that I want to position in a 2D space. I calculate an ideal position for each element. Now my problem is that many elements overlap as very often the ideal positions are concentrated in one region. I want to avoid overlap as much as possible (doesn't have to be perfect, though). How can I do this? I've heard physics simulations are suitable for this - is that correct? And can anyone provide an example/tutorial? By the way: I'm using XNA, if you know any .NET library that does exactly this job - tell me!

  Read the article

• Affine transformation algorithm.

  - by thehawk90

  Does anyone know of any standard algorithms to determine an affine transformation matrix based upon a set of known points in two co-ordinate systems?

  Read the article

• Simple encryption - Sum of Hashes in C

  - by Dogbert

  I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

  Read the article

< Previous Page | 61 62 63 64 65 66 67 68 69 70 71 72  | Next Page >