permutation | Permutation library in Ruby
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Permutation library in Ruby
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Trending Discussions on permutation
QUESTION
I'm trying to recreate the mean-median difference test described here: Archive of NYT article. I've downloaded House data from MIT's Election Lab, and pared it down to the 2012 Pennsylvania race. Using dplyr
, I whittled it down to the relevant columns, and it now looks something like this:
ANSWER
Answered 2022-Feb-09 at 23:58I figured it out! Randomly placing voters in each district is not correct, and honestly it was pretty silly of me to do so. Instead, I had to use dplyr
to create a data frame with the number of Democrat and Republican votes in each of the 435 House districts, one district per row. Then, I followed the advice on page 12 of this paper. I created samples of 18 districts sampled from this 435-row data frame, rejecting them if the mean vote share was more than 1 percent away from that of PA. The results have a much nicer 95% confidence interval, that matches the results of the original article.
QUESTION
I'm working on a statistics project involving cards and shuffling, and I've run across an issue with random number generation.
From a simple bit of math there are 52! possible deck permutations, which is approximately 2^226. I believe this means that I need a random number generator with a minimum of 226 bits of entropy, and possibly more (I'm not certain of this concept so any help would be great).
From a quick google search, the Math.random()
generator in Java has a maximum of 48 bits of entropy, meaning that the vast majority of possible deck combinations would not be represented. So this does not seem to be the way to go in Java.
I was linked to this generator but it doesn't have a java implementation yet. Also for a bit of context here is one of my shuffling algorithms (it uses the Fisher-Yates method). If you have any suggestions for better code efficiency that would be fantastic as well.
...ANSWER
Answered 2022-Jan-15 at 01:10Have you looked into the recent additions that are included in JDK 17?
There are plenty of algorithms available:
For shuffling cards you likely don't need something that is cryptographically secure.
Using Collections.shuffle should do the trick if you provide a decent RNG.
QUESTION
I want to turn this halting, discontinuous trails in the particle on this simulation
to something worth staring at as in this beautiful field flow in here (not my work, but I don't remember where I got it from).
I have tried different permutations of the code in the accomplished field flow without getting anything remotely close to the smoothness in the transitions that I was aiming for. I suspect I am mishandling the updates or the placement of the black rectangle that seems to circumvent the need for a black background, which would erase the wake of the particles.
...ANSWER
Answered 2022-Jan-11 at 17:55You can get trials in multiple ways. The sketch you mentioned creates the trails by adding opacity to the background with the "fill( 0, 10 )" function.
If you want to know more about p5 functions you can always look them up here: https://p5js.org/reference/. The fill() page shows that the first argument is the color ( 0 for black ) and the second argument is the opacity ( 10 out of 255 ).
In the sketch you mentioned, in draw(), they wrote:
QUESTION
Consider the following simplified example, with all possible 2 x 2 matrices with one 1 and the remaining 0s.
...ANSWER
Answered 2021-Dec-31 at 17:52You could use the function developed here to get all possible matrices of dim 5x4, and then filter by the number of 1s using sum
.
QUESTION
I have the following data:
...ANSWER
Answered 2021-Dec-30 at 20:32We'll use gtools::permutations
to calculate the ... permutations of inputs
, and then use expand.grid
to show all combinations within them.
First, we can do it easily on one order of the inputs with:
QUESTION
I would like to generate a list of all permutations of 4 digits where :
- All 4 digits are always present
- Two reversed sequences are the same solution. For example. (1,2,3,4) = (4,3,2,1)
I would like to know:
- What do you call this kind of permutations.
- If it is possible to generate this list in one step. Below there is an example that generates it in two steps.
ANSWER
Answered 2021-Nov-12 at 13:45To simplify your code and make it more efficient you could:
1- use a python set as the container (checking the presence of an element is much faster)
2- add the final output directly
3- avoid to create a temporary list with the permutations, keep it as a generator
QUESTION
I'm familiar with databases but have never used Oracle in particular. In the process of trying to help someone with a homework assignment, I've hit a snag trying to understand the behavior of the BREAK
command. In particular, the results of using the BREAK
command seem to depend on the order of the columns in the query I'm using, which as far as I can tell is not reflected in the documentation in any way.
I created a table where there are a couple of different colors, each with a few items of that color, like so:
...ANSWER
Answered 2021-Nov-11 at 07:49The behaviour of BREAK
in your example is not right. I update this post thanks to @Littlefoot, and is due to the fact that you are using a SqlDeveloper, a java tool not intended for this kind of reporting.
I created your table and insert the records in both databases, then running the reports you did.
Demo 12cR2
QUESTION
For my project, I need to come up with a TypeScript type, which is this so-called CardSize.
This type can take various forms. It can either be a static value, a responsive (breakpoint-specific) value, or a combination of either of them separated by a white space.
The possible (singular) values are as follows:
...ANSWER
Answered 2021-Nov-07 at 00:29You can definitely generate a union type of permutations/combinations of string values, recursively concatenated via template literal types. Of course, the number permutations and combinations grows quite rapidly as you increase the number of elements to permute and combine. TypeScript can only handle building unions on the order of tens of thousands of elements, and compiler performance tends to suffer when you get close to this. So this approach will only work for small numbers of elements.
Your CardSize
example will be fine because you only have two sizes and four breakpoints:
QUESTION
I wish to determine whether Java is running on Windows, and have seen many different suggestions which include various permutations of the System property os.name
with startsWith
/ indexOf
/ contains
/ toLowerCase(Locale.ENGLISH)
/ toLowerCase()
, or just File.separatorChar
.
I scanned JDK source code to see whether there was a definitive answer (see below) and a few other SO posts which suggest:
...ANSWER
Answered 2021-Nov-01 at 16:26After noting the various comments and other posts, I've not found a reason not to continue using the isWindows
check I currently have in my code, which is simply the first test listed:
QUESTION
Statement:
Given an array of strings S. You can make a string by combining elements from the array S (you can use an element more than once)
In some situations, there are many ways to make a certain string from the array S.
Example:
S = {a, ab, ba}
Then there are 2 ways to make the string "aba":
- "a" + "ba"
- "ab" + "a"
Question:
Given an array of string S. Find the shortest string such that there are more that one way to make that string from S. If there're none, print out -1.
P/S: I have been thinking for many days but this is the best one I've got so far:
- Generate all permutations of the array
- For each permutation, make a string from the array S
- Check if that string is made before, if yes, print out the string, if not, save that string.
But this algorithm clearly won't pass all the test cases. I can't think of any better algorithm.
...ANSWER
Answered 2021-Oct-31 at 15:28Here's an O(N3) algorithm, where N
is the total length of each string:
- For every element Si in S:
- Construct an NFA for the regular expression Si(S1|...|Sn)*
- Construct an NFA for the regular expression (S1|...|Si-1|Si+1|...|Sn)(S1|...|Sn)*
- Construct an NFA that is the intersection of the NFA in step 1.1 and step 1.2
- Find the shortest string accepted by the NFA in step 1.3
- Return the shortest string among the strings in step 1.4
The above algorithm can be improved to O(N2logN):
- Construct an NFA for the regular expression (S1|...|Sn)*
- Construct cross-product of two copies of the NFA in step 1.
- For each state in the NFA in step 2, find the shortest string accepted by the NFA from that state.
- Let 𝒮 = {S}.
- While 𝒮 is not empty:
- Take an element T from 𝒮.
- Partition T into P and Q somewhat evenly.
- Construct an NFA for the regular expression (P1|...|Pp)(S1|...|Sn)*, reusing the NFA in step 1.
- Construct an NFA for the regular expression (Q1|...|Qq)(S1|...|Sn)*, reusing the NFA in step 1.
- Construct cross-product of the NFA in step 5.3 and step 5.4, reusing the NFA in step 2.
- Find the shortest string accepted by the NFA in step 5.5, reusing the result of step 3.
- If P has more than 1 element, put P into 𝒮.
- If Q has more than 1 element, put Q into 𝒮.
- Return the shortest string among the strings in step 5.6
Edit: The following is an O(N2) algorithm, improved from the top answer:
- Let T be every suffix of every string of S.
- Build a trie out of T.
- Let G be a weighted directed graph. The vertices are the elements of T, and the edges are: for each string Si in S and Tj in T, if Si = Tj + D or Tj = Si + D (using the trie in step 2 to find all such pairs), add an edge from D to Tj weighted length of Si.
- Find the distance from the empty string to every vertex in G.
- For each string Si, Sj in S, if Si != Sj and Si = Sj + D (using the trie in step 2 to find all such pairs), find the distance from the empty string to D (using step 4).
- The length of the answer is half of the shortest distance among all distances in step 5. (It's trivial to find the actual answer but I'm too lazy to describe it :p)
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