# rrsigma

Compute relative density ratio

## Syntax

``s = rrsigma(rho,mach,g)``

## Description

example

````s = rrsigma(rho,mach,g)` computes the relative density ratio `s`, from the static densities `rho`, Mach numbers, `mach`, and specific heat ratios, `g`. ```

## Examples

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Determine the relative density ratio for three densities.

`sigma = rrsigma([1.225 0.3639 0.0953], 0.5, 1.4)`
```sigma = 1×3 1.1297 0.3356 0.0879 ```

Determine the relative density ratio for three densities and three different heat ratios.

`sigma = rrsigma([1.225 0.3639 0.0953], 0.5, [1.4 1.35 1.4])`
```sigma = 1×3 1.1297 0.3357 0.0879 ```

This example shows how to determine the relative density ratio for three densities at three different conditions.

`sigma = rrsigma([1.225 0.3639 0.0953], [0.5 1 2], [1.4 1.35 1.4])`
```sigma = 1×3 1.1297 0.4709 0.3382 ```

## Input Arguments

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M static densities, specified as a scalar or vector in kilograms per meter cubed.

Example: `[1.225 0.3639 0.0953]`

Data Types: `double`

M mach numbers, specified as a scalar or vector.

Example: `[0.5 1 2]`

Data Types: `double`

M specific heat ratios, specified as a scalar or vector.

Example: `[1.4 1.35 1.4]`

Data Types: `double`

## Output Arguments

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M density relative ratios, returned as a scalar or vector.

## Limitations

For cases in which total density ratio is desired (Mach number is nonzero), the total density is calculated assuming perfect gas (with constant molecular weight, constant pressure specific heat, and constant specific heat ratio) and dry air.

 Pratt & Whitney Aircraft. Aeronautical Vestpocket Handbook. United Technologies, August 1986.