Index

An index is an indirect shortcut derived from and pointing into a greater volume of values, data, information or knowledge. Index may refer to:

Business

Publishing

Database index

A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Indexes are used to quickly locate data without having to search every row in a database table every time a database table is accessed. Indexes can be created using one or more columns of a database table, providing the basis for both rapid random lookups and efficient access of ordered records.

An index is a copy of select columns of data from a table that can be searched very efficiently that also includes a low-level disk block address or direct link to the complete row of data it was copied from. Some databases extend the power of indexing by letting developers create indices on functions or expressions. For example, an index could be created on upper(last_name), which would only store the upper case versions of the last_name field in the index. Another option sometimes supported is the use of partial indices, where index entries are created only for those records that satisfy some conditional expression. A further aspect of flexibility is to permit indexing on user-defined functions, as well as expressions formed from an assortment of built-in functions.

Index (statistics)

In statistics and research design, an index is a composite statistic – a measure of changes in a representative group of individual data points, or in other words, a compound measure that aggregates multiple indicators. Indexes summarize and rank specific observations.

Much data in the field of social sciences is represented in various indices such as Gender Gap Index, Human Development Index or the Dow Jones Industrial Average.

Item in indexes are usually weighted equally, unless there are some reasons against it (for example, if two items reflect essentially the same aspect of a variable, they could have a weight of 0.5 each).

Constructing the items involves four steps. First, items should be selected based on their face validity, unidimensionality, the degree of specificity in which a dimension is to be measured, and their amount of variance. Items should be empirically related to one another, which leads to the second step of examining their multivariate relationships. Third, indexes scores are designed, which involves determining their score ranges and weights for the items. Finally, indexes should be validateds, which involves testing whether they can predict indicators related to the measured variable not used in their construction.

Grasshopper (rocket)

Grasshopper and the Falcon 9 Reusable Development Vehicles (F9R Dev) were experimental technology-demonstrator reusable rockets that make vertical takeoffs and vertical landings. The project was privately funded by SpaceX, with no funds provided by the government. Two prototypes were built, and both were launched from the ground.

Grasshopper was announced in 2011 and began low-altitude, low-velocity hover/landing testing in 2012. The initial Grasshopper test vehicle was 106 ft (32 m) tall and made eight successful test flights in 2012 and 2013 before being retired. A second Grasshopper-class prototype was the larger and more capable Falcon 9 Reusable Development Vehicle (F9R Dev, also known as F9R Dev1) based on the Falcon 9 v1.1 launch vehicle. It was tested at higher altitudes and supersonic speeds as well as providing additional low-altitude tests. The F9R Dev1 vehicle was built in 2013–2014 and made its first low-altitude flight test on 17 April 2014; it was lost during a three-engine test at the McGregor test site on 22 August 2014.

Grasshopper (chess piece)

The grasshopper is a fairy chess piece that moves along ranks, files, and diagonals (as an ordinary queen) but only by hopping over another piece at any distance to the square immediately closest. If there is no piece to hop over, it cannot move. If the square beyond a piece is occupied by a piece of the opposite color, the grasshopper can capture that piece. The grasshopper may jump over pieces of either color; the piece being jumped over is unaffected.

On the diagram it is shown as an inverted queen with notation G.

For an example of grasshopper movement see the first diagram. The white grasshopper on d4 can move to the squares marked with crosses (b2, d1, d7 and h8), as well as capture the black pawn on a7. It cannot move to g4, because there are two pieces to hop over.

The grasshopper was introduced by T. R. Dawson in 1913 in problems published in the Cheltenham Examiner newspaper. Nowadays it is one of the most popular fairy pieces used in chess problems.

Sample problem

Grasshopper (musician)

Grasshopper (born Sean Thomas Mackowiak, May 25 1967) is an American musician with the band Mercury Rev. He has also appeared with Rev side-project Harmony Rockets, his own band Grasshopper and the Golden Crickets, and as a guest musician on numerous other recordings.

Early years

Mackowiak's early years have been colored by a 1991 interview given to music publication Melody Maker, which claimed that he met Rev singer Jonathan Donahue in Camp Sunshine, a reform camp for juvenile delinquents, at the age of ten.

Grasshopper was throwing dead squirrels and rats into a lawnmower when Jonathan met him. The blood spattered over a watching group of retarded kids and they screamed and yelled. They yelled, "Now throw the possum in! The Possum! The possum too!" Muses Jonathan, "When you're younger, these things make a more vivid impression. I remember huge adrenaline rushes as the guts flew and hit people on the legs. I don't know what Grasshopper had done to get in there. He doesn't talk about it much."