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## Description

Rspeed = radialspeed(Pos,V) returns the radial speed of the given platforms relative to a reference platform. The platforms have positions Pos and velocities V. The reference platform is stationary and is located at the origin.

Rspeed = radialspeed(Pos,V,RefPos) specifies the position of the reference platform.

Rspeed = radialspeed(Pos,V,RefPos,RefV) specifies the velocity of the reference platform.

## Input Arguments

 Pos Positions of platforms, specified as a 3-by-N matrix. Each column specifies a position in the form [x; y; z], in meters. V Velocities of platforms, specified as a 3-by-N matrix. Each column specifies a velocity in the form [x; y; z], in meters per second. RefPos Position of reference platform, specified as a 3-by-1 vector. The vector has the form [x; y; z], in meters. Default: [0; 0; 0] RefV Velocity of reference platform, specified as a 3-by-1 vector. The vector has the form [x; y; z], in meters per second. Default: [0; 0; 0]

## Output Arguments

 Rspeed Radial speed in meters per second, as an N-by-1 vector. Each number in the vector represents the radial speed of the corresponding platform. Positive numbers indicate that the platform is approaching the reference platform. Negative numbers indicate that the platform is moving away from the reference platform.

## Examples

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### Radial Speed of Target Relative to Stationary Platform

Calculate the radial speed of a target relative to a stationary platform. Assume the target is located at [20; 20; 0] meters and is moving with velocity [10; 10; 0] meters per second. The reference platform is located at [1; 1; 0].

`rspeed = radialspeed([20; 20; 0],[10; 10; 0],[1; 1; 0]);`