unique

问题 This question already has answers here : Finding ALL duplicate rows, including “elements with smaller subscripts” (5 answers) Remove all duplicate rows including the “reference” row [duplicate] (3 answers) Closed 4 years ago . For example I have two columns: Var1 Var2 1 12 1 65 2 68 2 98 3 49 3 24 4 8 5 67 6 12 And I need to display only values which are unique for column Var1: Var1 Var2 4 8 5 67 6 12 I can do you like this: mydata=mydata[!unique(mydata$Var1),] But when I use the same formula

问题 I was wondering what was the most concise way to get an array of a certain size, of unique random numbers. I get random numbers like this: times(4, () => random(30, 95)); However this is not unique. I can filter this with uniq but I need to gurantee length of 4 of array. And I want to do it the lodash way. Any ideas? 回答1: I know this isn't "the lodash way", but it guarantees uniqueness, and allows you to use the same arguments as you were using before. It also scales better than methods that

问题 I have two primary (composite) keys that refer to a shop and a branch. I thought I should have used a corresponding ID for each row, so I added a UNIQUE + AUTO_INCREMENT named ID. So I had on the table a column named ID (AUTO INCREMENT), but it was declared PRIMARY - which was done automatically, and I don't want the ID to be PRIMARY. Just the shop and branch. I have learnt how to trick MYSQL to accept the ID field as UNIQUE and AUTO INCREMENT, as it was not extremely trivial to make the AUTO

问题 I've two strings StringA, StringB. I want to generate a unique string to denote this pair. i.e. f(x, y) should be unique for every x, y and f(x, y) = f(y, x) where x, y are strings. Any ideas? 回答1: Compute a message digest of both strings and XOR the values MD5(x) ^ MD5(Y) The message digest gives you unique value for each string and the XOR makes it possible for f(x, y) to be equal to f(y, x). EDIT: As @Phil H observed, you have to treat the case in which you receive two equal strings as

问题 WARNING: CPU Usage goes to 100%, be careful. Link to the jsFiddle This script has been written to design a dynamic snake and ladder board. Everytime the page is refreshed a new board is created. Most of the time all of the background images do not appear, and the CPU usage goes up to 100%. But on occasion all of them appear and the CPU usage is normal. Opera shows some of the background images, Firefox lags and asks me if I wish to stop the script. I believe that the problem is with these

问题 I've been using MongoDB with C#, and have been using ObjectIds, then later GUIDs for my Entity Ids. I hate looking at these Id's, I think it's counter intuitive... I'd really like to be able to use integers or longs, like relational DBs Identity column. But I'm having a hard time finding a way to do it. If I use collection max + 1, that will lead to race conditions. I've read about using a Hi-Lo Generator algorithm, but how does that work? What if I have 10 app servers running the same code?

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Easiest way to find duplicate values in a JavaScript array Javascript array sort and unique I have the following array var output = new array(7); output[0]="Rose"; output[1]="India"; output[2]="Technologies"; output[3]="Rose"; output[4]="Ltd"; output[5]="India"; output[6]="Rose"; how can i remove the duplicate elements in above array.Is there any methods to do it? 回答1: You can write a function like this function

问题 I have a data set with districts, counties and years. If a given district/county combination occurs in any year I want that combination to occur in every year. Below are two ways I have figured out to do this. The first approach uses a function to create combinations of district, county and year and only requires six lines of code. The bottom approach uses a combination of paste , expand.grid and strsplit and is much more complex/convoluted. There are probably much more efficient methods than

问题 I know there are many answers about returning unique values in an array after removing duplicates, but isn't every element in an array unique after you remove the duplicates? I want to only return values that are unique prior to removing any duplicates. If the element repeats in the original array, I don't want it in my final array. So this array... [0, 1, 1, 2, 3, 3, 3, 4] should return only: [0, 2, 4] Another way to phrase this would be to remove all duplicates as well as all unique values

问题 Given the following data frame: import pandas as pd d=pd.DataFrame({'label':[1,2,2,2,3,4,4], 'values':[3,5,7,2,5,8,3]}) d label values 0 1 3 1 2 5 2 2 7 3 2 2 4 3 5 5 4 8 6 4 3 I know how to count the unique values like this: d['dup']=d.groupby('label')['label'].transform('count') Which results in: label values dup 0 1 3 1 1 2 5 3 2 2 7 3 3 2 2 3 4 3 5 1 5 4 8 2 6 4 3 2 But what I would like is a column to have the following values: 1 if there is 1 unique row per the label column, 2 if there