040-Variance.md

QuickData.Core.FSharp

Variance

This type is a value which is clamped to the range of -1.0 to +1.0 (inclusive).

• The Variance Module
  • Operators
  • Construction Functions
  • Deconstruction Functions
  • Variation Functions
  • Ready-made Values
  • Code Examples
• Issues, Questions, and Suggestions

The Variance Module

The Variance module provides operators and functions for working with a Variance.

Note: When a Variance is printed via structured formatting - e.g. printf "%A" - the value will be prefixed with a 'V', e.g. V0.5. You would not usually print a Variance but this might be useful to know.

Operators

The operators provided are:

• * : Multiplies one Variance by another Variance, or by a Normal, returning a new Variance.

The methods provided are:

• Value : Returns the value of a Variance as a float (equivalent to the toFloat function).

Construction Functions

The construction functions provided are:

• fromFloat : The only way you can manually create a Variance;
• fromNormal : Creates a new Variance directly from the value of a Normal;
• fromNormalSpread : Creates a new Variance from the value of a Normal (value is recalculated).

Deconstruction Functions

The deconstruction functions provided are:

• toFloat : Returns the value of a Variance as a float (equivalent to the Value method);
• toNormal : Creates a new Normal directly from the value of a Variance;
• toNormalSpread : Creates a new Normal from the value of a Variance (value is recalculated).

Variation Functions

The variation functions provided are:

• invert : Creates a new Variance which is an inversion of the original.

Inverting a Variance takes the value of the original, gets the negative of that value (producing a positive if the original value was negative), and then creates a new Variance from that new value.

Ready-made Values

The Variance module also provides various ready-made values which make it easy to specify some often-used Variances.

These values are:

• minimum = -1.0 ; the lowest possible value;
• zero = 0.0;
• maximum = +1.0 ; the highest possible value.

Code Examples

let okayPositive = Variance.fromFloat 0.7 // -> Variance 0.7 

let okayNegative = Variance.fromFloat -0.3 // -> Variance -0.3 

let invertedVariance = 
    Variance.fromFloat 0.4 
    |> Variance.invert // -> Variance -0.4 

let ofNormal = 
    Normal.fromFloat 0.2 
    |> Variance.fromNormal // -> Variance 0.2 

let ofNormalSpread = 
    Normal.fromFloat 0.2 
    |> Variance.fromNormalSpread // -> Variance -0.6

Issues, Questions, and Suggestions

You can visit the QuickData.FSharp GitHub repository to report issues, ask questions, or make suggestions. You can also read about the changes across different versions in the release notes there.