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  2. Dataframe - Wikipedia

    en.wikipedia.org/wiki/Dataframe

    Dataframe may refer to: A tabular data structure common to many data processing libraries: pandas (software) § DataFrames; The Dataframe API in Apache Spark; Data frames in the R programming language; Frame (networking)

  3. Polar set - Wikipedia

    en.wikipedia.org/wiki/Polar_set

    The real polar of a subset of is the set: := { : ⁡ , } and the real prepolar of a subset of is the set: := { : ⁡ , }.. As with the absolute prepolar, the real prepolar is usually called the real polar and is also denoted by . [2] It's important to note that some authors (e.g. [Schaefer 1999]) define "polar" to mean "real polar" (rather than "absolute polar", as is done in this article) and ...

  4. Cylindrical coordinate system - Wikipedia

    en.wikipedia.org/wiki/Cylindrical_coordinate_system

    The three coordinates (ρ, φ, z) of a point P are defined as: The radial distance ρ is the Euclidean distance from the z-axis to the point P.; The azimuth φ is the angle between the reference direction on the chosen plane and the line from the origin to the projection of P on the plane.

  5. Polar coordinate system - Wikipedia

    en.wikipedia.org/wiki/Polar_coordinate_system

    Hipparchus. The concepts of angle and radius were already used by ancient peoples of the first millennium BC.The Greek astronomer and astrologer Hipparchus (190–120 BC) created a table of chord functions giving the length of the chord for each angle, and there are references to his using polar coordinates in establishing stellar positions. [2]

  6. Polar Satellite Launch Vehicle - Wikipedia

    en.wikipedia.org/wiki/Polar_Satellite_Launch_Vehicle

    The 2.8 m (9 ft 2 in) diameter motor case is made of maraging steel and has an empty mass of 30,200 kg (66,600 lb). [ 9 ] Pitch and yaw control during first stage flight is provided by the Secondary Injection Thrust Vector Control (SITVC) System, which injects an aqueous solution of strontium perchlorate into the S139 exhaust divergent from a ...

  7. Polar bear - Wikipedia

    en.wikipedia.org/wiki/Polar_bear

    The polar bear (Ursus maritimus) is a large bear native to the Arctic and nearby areas. It is closely related to the brown bear, and the two species can interbreed.The polar bear is the largest extant species of bear and land carnivore, with adult males weighing 300–800 kg (660–1,760 lb).

  8. Polar regions of Earth - Wikipedia

    en.wikipedia.org/wiki/Polar_regions_of_Earth

    Visualization of the ice and snow covering Earth's northern and southern polar regions Northern Hemisphere permafrost (permanently frozen ground) in purple. The polar regions, also called the frigid zones or polar zones, of Earth are Earth's polar ice caps, the regions of the planet that surround its geographical poles (the North and South Poles), lying within the polar circles.