Minor cleanup

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Ozzie Gooen 2022-05-01 08:09:34 -04:00
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commit ed5b7e63f2

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---
title: "Creating Distributions"
title: "Distribution Creation"
sidebar_position: 8
---
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## To
`(5thPercentile: float) to (95thPercentile: float)`
`to(5thPercentile: float, 95thPercentile: float)`
`(5thPercentile: number) to (95thPercentile: number)`
`to(5thPercentile: number, 95thPercentile: number)`
The `to` function is an easy way to generate simple distributions using predicted _5th_ and _95th_ percentiles.
@ -44,8 +44,8 @@ If both values are above zero, a `lognormal` distribution is used. If not, a `no
### Arguments
- `5thPercentile`: Float
- `95thPercentile`: Float, greater than `5thPercentile`
- `5thPercentile`: number
- `95thPercentile`: number, greater than `5thPercentile`
<Admonition type="tip" title="Tip">
<p>
@ -68,8 +68,8 @@ If both values are above zero, a `lognormal` distribution is used. If not, a `no
## Mixture
`mixture(...distributions: Distribution[], weights?: float[])`
`mx(...distributions: Distribution[], weights?: float[])`
`mixture(...distributions: Distribution[], weights?: number[])`
`mx(...distributions: Distribution[], weights?: number[])`
The `mixture` mixes combines multiple distributions to create a mixture. You can optionally pass in a list of proportional weights.
@ -87,8 +87,8 @@ The `mixture` mixes combines multiple distributions to create a mixture. You can
### Arguments
- `distributions`: A set of distributions or floats, each passed as a paramater. Floats will be converted into Delta distributions.
- `weights`: An optional array of floats, each representing the weight of its corresponding distribution. The weights will be re-scaled to add to `1.0`. If a weights array is provided, it must be the same length as the distribution paramaters.
- `distributions`: A set of distributions or numbers, each passed as a paramater. Numbers will be converted into Delta distributions.
- `weights`: An optional array of numbers, each representing the weight of its corresponding distribution. The weights will be re-scaled to add to `1.0`. If a weights array is provided, it must be the same length as the distribution paramaters.
### Aliases
@ -100,7 +100,7 @@ The `mixture` mixes combines multiple distributions to create a mixture. You can
<summary>🕐 Zero or Continuous</summary>
<p>
One common reason to have mixtures of continous and discrete distributions is to handle the special case of 0.
Say I want to model the time I will spend on some upcoming assignment. I think I have an 80% chance of doing it.
Say I want to model the time I will spend on some upcoming project. I think I have an 80% chance of doing it.
</p>
<p>
@ -120,10 +120,6 @@ mx(hours_the_project_will_take, 0, [chance_of_doing_anything, 1 - chance_of_doin
"just-in-case distribution". This latter distribution would have very low weight, but would be
very wide, just in case they were dramatically off for some weird reason.
</p>
<p>
One common reason to have mixtures of continous and discrete distributions is to handle the special case of 0.
Say I want to model the time I will spend on some upcoming assignment. I think I have an 80% chance of doing it.
</p>
<SquiggleEditor
initialSquiggleString={`forecast = 3 to 30
chance_completely_wrong = 0.05
@ -135,7 +131,7 @@ mx(forecast, forecast_if_completely_wrong, [1-chance_completely_wrong, chance_co
## Normal
`normal(mean:float, standardDeviation:float)`
`normal(mean:number, standardDeviation:number)`
Creates a [normal distribution](https://en.wikipedia.org/wiki/Normal_distribution) with the given mean and standard deviation.
<Tabs>
@ -149,29 +145,28 @@ Creates a [normal distribution](https://en.wikipedia.org/wiki/Normal_distributio
### Arguments
- `mean`: Float
- `standard deviation`: Float greater than zero
- `mean`: Number
- `standard deviation`: Number greater than zero
[Wikipedia](https://en.wikipedia.org/wiki/Normal_distribution)
## Log-normal
`lognormal(mu: float, sigma: float)`
`lognormal(mu: number, sigma: number)`
Creates a [log-normal distribution](https://en.wikipedia.org/wiki/Log-normal_distribution) with the given mu and sigma.
`Mu` and `sigma` can be difficult to directly reason about. Because of this complexity, we recommend typically using the <a href="#to">to</a> syntax instead of estimating `mu` and `sigma` directly.
<SquiggleEditor initialSquiggleString="lognormal(0, 0.7)" />
### Arguments
- `mu`: Float
- `sigma`: Float greater than zero
- `mu`: Number
- `sigma`: Number greater than zero
[Wikipedia](https://en.wikipedia.org/wiki/Log-normal_distribution)
### Argument Alternatives
`Mu` and `sigma` can be difficult to directly reason about. Because of this complexity, we recommend typically using the <a href="#to">to</a> syntax.
<details>
<summary>❓ Understanding <bold>mu</bold> and <bold>sigma</bold></summary>
<p>
@ -187,15 +182,15 @@ logOfLognormal = log(lognormal(normalMean, normalStdDev))
## Uniform
`uniform(low:float, high:float)`
`uniform(low:number, high:number)`
Creates a [uniform distribution](https://en.wikipedia.org/wiki/Uniform_distribution_(continuous)) with the given low and high values.
<SquiggleEditor initialSquiggleString="uniform(3,7)" />
### Arguments
- `low`: Float
- `high`: Float greater than `low`
- `low`: Number
- `high`: Number greater than `low`
<Admonition type="caution" title="Caution">
<p>
@ -208,7 +203,7 @@ Creates a [uniform distribution](https://en.wikipedia.org/wiki/Uniform_distribut
</Admonition>
## Beta
``beta(alpha:float, beta:float)``
``beta(alpha:number, beta:number)``
Creates a [beta distribution](https://en.wikipedia.org/wiki/Beta_distribution) with the given `alpha` and `beta` values. For a good summary of the beta distribution, see [this explanation](https://stats.stackexchange.com/a/47782) on Stack Overflow.
@ -232,8 +227,8 @@ Creates a [beta distribution](https://en.wikipedia.org/wiki/Beta_distribution) w
### Arguments
- `alpha`: Float greater than zero
- `beta`: Float greater than zero
- `alpha`: Number greater than zero
- `beta`: Number greater than zero
<Admonition type="caution" title="Caution with small numbers">
<p>
@ -260,39 +255,37 @@ Creates a [beta distribution](https://en.wikipedia.org/wiki/Beta_distribution) w
## Exponential
``exponential(rate:float)``
``exponential(rate:number)``
Creates an [exponential distribution](https://en.wikipedia.org/wiki/Exponential_distribution) with the given rate.
<SquiggleEditor initialSquiggleString="exponential(4)" />
### Arguments
- `rate`: Float greater than zero
- `rate`: Number greater than zero
## Triangular distribution
``triangular(low:float, mode:float, high:float)``
``triangular(low:number, mode:number, high:number)``
Creates a [triangular distribution](https://en.wikipedia.org/wiki/Triangular_distribution) with the given low, mode, and high values.
#### Validity
### Arguments
- `low`: Float
- `mode`: Float greater than `low`
- `high`: Float greater than `mode`
- `low`: Number
- `mode`: Number greater than `low`
- `high`: Number greater than `mode`
<SquiggleEditor initialSquiggleString="triangular(1, 2, 4)" />
## FromSamples
``fromSamples(samples:number[])``
Creates a sample set distribution using an array of samples.
<SquiggleEditor initialSquiggleString="fromSamples([1,2,3,4,6,5,5,5])" />
#### Validity
For `fromSamples(xs)`,
- `xs.length > 5`
- Strictly every element of `xs` must be a number.
### Arguments
- `samples`: An array of at least 5 numbers.