indexing

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: How can I change the values of multiple points in a matrix? I have a matrix A and three vectors of the same length, r , holding the indexes of the rows to assign to, c , holding the indexes of the columns to assign to, and v containing the actual values to assign. What I want to get is A(r(i),c(i))==v(i) for all i . But doing A(r,c)=v; Doesn't yield the correct result as matlab interprets it as choosing every

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: How can I change the values of multiple points in a matrix? I have a matrix A and three vectors of the same length, r , holding the indexes of the rows to assign to, c , holding the indexes of the columns to assign to, and v containing the actual values to assign. What I want to get is A(r(i),c(i))==v(i) for all i . But doing A(r,c)=v; Doesn't yield the correct result as matlab interprets it as choosing every

问题 I'm an intermediate user in jQuery. I know to find the rowIndex of a table using jQUery, but my scenario is a different one. My table(GridView) consists of 20 columns and each column with different controls like textbox, dropdownlist, image, label. All are server side controls in each row. I bind the gridview with the records from the database. Now when I click on any control or onchange of any textbox, I need to get the rowIndex of that changed column's row. Here is the code I've user: $("

问题 Fetching of attributes in WordPress (using MySQL) seems to be slower than necessary. (This is a self-answered question, so proceed to my answer.) 回答1: The standard schema for wp_postmeta provides poor indexes. This leads to performance problems. By changing the schema to this, most references to meta data will be faster: CREATE TABLE wp_postmeta ( post_id …, meta_key …, meta_value …, PRIMARY KEY(post_id, meta_key), INDEX(meta_key) ) ENGINE=InnoDB; Notes: The current AUTO_INCREMENT column is a

问题 Let's say I have a function, like: function [result] = Square( x ) result = x * x; end And I have an array like the following, x = 0:0.1:1; I want to have an y array, which stores the squares of x 's using my Square function. Sure, one way would be the following, y = zeros(1,10); for i = 1:10 y(i) = Square(x(i)); end However, I guess there should be a more elegant way of doing it. I tried some of my insights and made some search, however couldn't find any solution. Any suggestions? 回答1: For

问题 I'm using PostgreSQL 9.3 version to create database. I have the following table test with some columns list. create table test ( cola varchar(10), colb varchar(10), colc varchar(10), cold varchar(10) ); Now I want to create a indexs on some columns. For example: I want to create clustered index for columns cola and colb . And I want to create non clustered index for columns colc and cold . As I referred this And this ,I come to know that there is no clustered and non clustered index in

问题 I want to create Index on Mongo database for performance prespective, so could you please help me how I can do it? Your help will be appreciated here. 回答1: Before applying indexing in mongodb collections you need to understand the following aspects of indexing: Indexing strategy: Check your application for what type of queries does it send to mongodb. List down all such possible queries. Based on the number of operations, type of operations define index type Choose the correct type of indexes

问题 I can't seem to find the reasoning behind the behaviour of .loc. I know it is label based, so if I iterate over Index object the following minimal example should work. But it doesn't. I googled of course but I need additional explanation from someone who has already got a grip on indexing. import datetime import pandas as pd dict_weekday = {1: 'MON', 2: 'TUE', 3: 'WED', 4: 'THU', 5: 'FRI', 6: 'SAT', 7: 'SUN'} df = pd.DataFrame(pd.date_range(datetime.date(2014, 1, 1), datetime.date(2014, 1, 15

问题 I have added a FULLTEXT index to one of my MySQL database tables as follows: ALTER TABLE members ADD FULLTEXT(about,fname,lname,job_title); The problem is that using phpmyadmin I can see the cardinality of my new index is only 1 . Does this mean the index will never be used? I have run a analyze table command but it didn't seem to do anything. analyze table members The respective types of the index fields are varchar(100), varchar(100), text, varchar(200) and the engine used is MyISAM and the

问题 I'm very new to R (and programming in general) and I've been stuck on this (probably very easy) question for a few days... How would one make the vector 3 6 12 24 48 96 192 384 768 with a for loop? All I've managed to come up with so far is something along the lines of: x=numeric() for (i in 1:8) (x=2*i[-1]) However, that doesn't work. I think one of the main problems is that I don't understand how to index numbers in a sequence. If anyone could point me in the right direction that would be