Re: Association Rule Algorithm:dynamic god capabilities. - Algorithms Discussion Boards

Re: Optimize algorithm arrange an array with items with even-indexs are on left side of array, items with odd-indexs are on right side of array

Richard MacCutchan1-Dec-15 2:47

Richard MacCutchan

1-Dec-15 2:47

It is a fairly straghtforward matter of taking all the even numbered items (0, 2, 4 etc) first, followed by the odds.

Re: Optimize algorithm arrange an array with items with even-indexs are on left side of array, items with odd-indexs are on right side of array

Patrice T1-Dec-15 8:32

Patrice T

1-Dec-15 8:32

can you show what you have done so far ?
Your request look like HomeWork !

Patrice

“Everything should be made as simple as possible, but no simpler.” Albert Einstein

modified 1-Dec-15 16:51pm.

Re: Optimize algorithm arrange an array with items with even-indexs are on left side of array, items with odd-indexs are on right side of array

Hồng Chấn Phát1-Dec-15 16:06

Hồng Chấn Phát

1-Dec-15 16:06

I have been developer for 5 years, I am not a student, so it's not homework ...

Re: Optimize algorithm arrange an array with items with even-indexs are on left side of array, items with odd-indexs are on right side of array

Patrice T1-Dec-15 16:18

Patrice T

1-Dec-15 16:18

Hồng Chấn Phát wrote:
I have been developer for 5 years, I am not a student, so it's not homework ...

Can you show what you have done ?

Patrice

“Everything should be made as simple as possible, but no simpler.” Albert Einstein

Re: Optimize algorithm arrange an array with items with even-indexs are on left side of array, items with odd-indexs are on right side of array

Daniel Pfeffer1-Dec-15 21:54

Daniel Pfeffer

1-Dec-15 21:54

I don't know if there is a general solution, but using swaps I have come up with:

N = 2 requires 0 swaps (obviously)
N = 4 requires 1 swap
N = 6 requires 3 swaps
N = 4 requires 4 swaps
N = 10 requires 6 swaps
...

Basically, moving the N/2 first elements of the pairs to the beginning requires N/2-1 swaps. The N/2 second elements are "nearly" in order, requiring only a few additional swaps.

If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack.

--Winston Churchill

Re: Optimize algorithm arrange an array with items with even-indexs are on left side of array, items with odd-indexs are on right side of array

BillWoodruff5-Dec-15 20:31

BillWoodruff

5-Dec-15 20:31

using System.Linq;

private int[] ints = new int[]{0,1,2,3,4,5,6,7,8,9,10};

// in some method
int[] sints = ints.Where(val => (val%2 == 0)).Concat(ints.Where(val => (val%2 == 1))).ToArray();

I'm not claiming that is optimal in terms of speed of code execution; but it's faster in terms of my valuable time writing code !

If I could not use Linq:

private string[] strs = new string[]{"a1","b1","a2","b2","a3","b3","a4","b4"};

private string firstOddValue = strs[1];

// in some method
List<string> strList = new List<string>{strs[0]};

for (int i = 1; i < strs.Length; i++)
{
    if (i%2 == 1)
    {
        strList.Add(strs[i]);
    }
    else
    {
        strList.Insert(strList.IndexOf(firstOddValue), strs[i]);
    }
}

«I want to stay as close to the edge as I can without going over. Out on the edge you see all kinds of things you can't see from the center» Kurt Vonnegut.

Association Rule Algorithm:dynamic god capabilities.

shuga25-Nov-15 6:16

shuga

25-Nov-15 6:16

Hi I have a dataset and I want to perform Association Rules on it.
In other for it to predict accurately, the algorithm should have the ability to look at each attribute and decipher their association which mostly is a result of activities between each attribute in the form of multiplication, addition, subtraction, re-appearance of common patterns etc

Common association algorithms follow a basic pattern deciphering method...'comparing the re-occurrence of item sets'....
The association algorithm I have in mind should have a dynamic god capability....it should be able to determine the relationship between the attributes by going deeper such as finding out if the multiplication of the data 'value' of an instance in one attribute with another data value of an instance in another attribute has a higher rate of predictive accuracy....my workflow is in WEKA and so a compatible algorithm is needed.

I will love to interact with any coder who believes such a task can be accomplished.

cheers

Re: Association Rule Algorithm:dynamic god capabilities.

Patrice T28-Nov-15 10:05

Patrice T

28-Nov-15 10:05

Have you done something or it is just an idea ?

Patrice

“Everything should be made as simple as possible, but no simpler.” Albert Einstein

Re: Association Rule Algorithm:dynamic god capabilities.

shuga28-Nov-15 17:57

shuga

28-Nov-15 17:57

Its an idea for mining out patterns that is evident in football data.

Re: Association Rule Algorithm:dynamic god capabilities.

shuga28-Nov-15 17:57

shuga

28-Nov-15 17:57

Its an idea for mining out patterns that is evident in football data.

Re: Association Rule Algorithm:dynamic god capabilities.

shuga28-Nov-15 17:57

shuga

28-Nov-15 17:57

Its an idea for mining out patterns that is evident in football data.

How do I solve the recurrence T(n) = T (n - 1) + c substitution method?

axeemg17-Nov-15 4:12

axeemg

17-Nov-15 4:12

How do I solve the recurrence T(n) = T (n - 1) + c substitution method?

Re: How do I solve the recurrence T(n) = T (n - 1) + c substitution method?

Patrice T17-Nov-15 17:53

Patrice T

17-Nov-15 17:53

Looks like a partial definition of a linear suite.
What do you want to solve ?

Patrice

“Everything should be made as simple as possible, but no simpler.” Albert Einstein

Algorithm query + request

Member 1214387716-Nov-15 6:53

Member 12143877

16-Nov-15 6:53

I have thought of an algorithm that would really aide the work I am doing but cannot think of a name for it to search if there is an online algorithm created for it that I could use.

Algorithm example + explanation: For the work I am doing I have lots of different amounts of money and a total figure. I know that the sum of some of these amounts will equal the total figure but I have no clue which amounts they are and am not too sure how many of these figures would reach the total. I would input the amounts of money and the total figure and the algorithm would have to evaluate every single combination of these amounts of money until it reached the total amount and would output which amounts of money were used to create that total.

I am not asking anyone to create this algorithm I am just asking whether there is a website with this algorithm on it that I could use or if this algorithm is really easy to create + therefore I could create it for myself.

Any comments would be helpful + please ask if you have any queries for clarity! Many thanks!

Re: Algorithm query + request

C^hris L^osinger16-Nov-15 7:01

C^hris L^osinger

16-Nov-15 7:01

this is the "coin change problem".

but, it's not an exceptionally hard problem. and it's probably worth trying to think it through on your own.

image processing toolkits | batch image processing

Re: Algorithm query + request

Patrice T17-Nov-15 18:00

Patrice T

17-Nov-15 18:00

You have a set of data, and you search which subset will match a criteria.
This is a classical problem, I am not sure there is a name to this problem, or as mentioned in previous answer, it is related to the coin change problem.

Patrice

“Everything should be made as simple as possible, but no simpler.” Albert Einstein

Hash table load factor

Member 1180386012-Nov-15 13:04

Member 11803860

12-Nov-15 13:04

Hi.

I was recently interested in literature regarding what a good hash table load factor is for rehashing. Wikipedia mentions 0,7, 0,75 and 2/3, but with no explanation as to why performance degrades at these numbers.

The problem intrigued me, and I came to the conclusion that, mathematically speaking, the load factor threshold is at exactly log 2 (~0,7), which I found rather beautiful in it's own way.

I am posting this in case somebody else finds it interesting as I could not find any reference to a similar solution. Please also reply if you find any errors.

---------------------------------------

Chaining can be avoided and branch prediction exploited by predicting if a bucket is empty or not. A bucket is probably empty if the probability of it being empty exceeds 0,5.

Let s represent the size and n the number of keys added. Using the binomial theorem, the probability of a bucket being empty is:

P(0) = C(n, 0) * (1/s)^0 * (1 - 1/s)^(n - 0).

Thus, a bucket is probably empty if there are less than

log(2)/log(s/(s - 1)) keys.

As s reaches infinity and if the number of keys added is such that P(0) = 0,5, then n/s approaches log(2) rapidly:

lim (log(2)/log(s/(s - 1)))/s as s -> infinity = log(2) ~ 0,7.

Algorithm needed to find a point on A4 size plane

Member 1213438812-Nov-15 3:45

Member 12134388

12-Nov-15 3:45

Distance given to a point on plane of A4 size. How to find X, Y if L1 and L2 (distances are given) ?

here is a link to image : http://s11.postimg.org/wymbahpxv/Xand_Y.png[^]

X1=55mm

Any ideas ?

Re: Algorithm needed to find a point on A4 size plane

Richard Deeming12-Nov-15 4:05

Richard Deeming

12-Nov-15 4:05

Split the larger triangle into two right-angled triangles, and apply Pythagoras:

<br />
L1² = x² + y²<br />
L2² = (X1 - x)² + y² = X1² - 2·X1·x + x² + y²<br />
<br />
L2² - L1² = X1² - 2·X1·x<br />
2·X1·x = X1² - L2² + L1²<br />
<br />
x = (X1² - L2² + L1²) / 2·X1<br />
<br />
y = ± √(L1² - x²)<br />

NB: there will be two solutions - one with a positive value for y, and one with a negative value.

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

Re: Algorithm needed to find a point on A4 size plane

Chris Maunder12-Nov-15 4:15

Chris Maunder

12-Nov-15 4:15

Use Pythagoras.

Let Pen tip = P. We know L1, L2, X1.

Define line segments R1 -> P = L1, R1 -> x = A, (x,0) -> P = B.

A² + B² = L1²

We know the length of A is X, since it's (0,0) -> (x,0), and we know length of B is y, since it's (x,0) to (x,y)

x² + y² = L1²

Let R2 -> P = L2, x -> R2 = C

B² + C² = L2²

A + C = X1 => C = X1 - A

So we have

x² + y² = L1²
y² + (X1 - x)² = L2²

Solve these and you get x and y

cheers
Chris Maunder

Fastest way to count nested loops

Member 113783027-Nov-15 2:32

Member 11378302

7-Nov-15 2:32

Im inputing three numbers of users choice
number 1
number 2
final number

what i want to find out is , how many combinations of number 1 and number 2 would result in final number = number1 *x + number2*y = final number.

I am using nested loops

Objective-C

int i;
int j;
long long int pocet=0; // the numbers of combination
long long int one; // first number inputed by user
long long int two; // second number inputed by user
long long int last; // final number inputed by user - wanted result
long long int one_max;
long long int two_max;
long long int add=1; //for incrementing loops
long long int reduc=1; // for decrementing loops

if((one%2==0) && (two%2==0)){
        if(one>two){
            add=two/2;
            reduc=one/2;
    }
}
one_max=last/one;
two_max=last/two;
for(i=0;i<=one_max;i+=add){
    for(j=two_max;j>=0;j-=reduc){
        long long int tmp_one=(one*i);
        long long int tmp_two=(two*j);
            if(tmp_one+tmp_two==last){
                two_max=j;
                pocet++;
        }
    }
}

if i input these numbers
one = 10;
two = 13;
final =100;
the only possible combination of first two numbers to result in final number is
10 * 10 + 13 * 0

modified 7-Nov-15 11:37am.

Re: Fastest way to count nested loops

Patrice T7-Nov-15 4:57

Patrice T

7-Nov-15 4:57

First of all, I fear your code don't work or is not complete.

Patrice

“Everything should be made as simple as possible, but no simpler.” Albert Einstein

Re: Fastest way to count nested loops

Member 113783027-Nov-15 5:02

Member 11378302

7-Nov-15 5:02

this is not full code , its just half pseudo code for illustrating my problem , i can provide full code if it helps