Custom Ranking - Other/REST Feed API Docs

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Stream allows you to configure your own ranking method. You can add multiple ranking methods to a given feed group.

Ranked feeds are only available on paid plans. Contact support after upgrading your account to enable ranked feeds for your organization.

An example ranking config is shown below:

Available Functions

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name	description
Basic Arithmetic	The following are supported: + - * / ( ) ^
ln(x)	Log Function natural base
log(x)	Log Function base 10
sin(x)	Trigonometric sine function
cos(x)	Trigonometric cosine function
tan(x)	Trigonometric tangent function
abs(x)	Absolute value
min(a,b)	Minimum value
max(a,b)	Maximum value
trunc(x)	Truncates to the nearest integer value
round(x)	Rounds to the nearest integer value
decay_linear(t)	Linear Decay
decay_exp(t)	Exponential Decay
decay_gauss(t)	Gauss Decay
rand_normal()	Returns a normally distributed number in the range [-inf, +inf] with standard normal distribution (stddev = 1, mean = 0)
rand_normal(a,b,σ,µ)	Returns a normally distributed number in the range [a, b] with specific normal distribution (stddev = σ, mean = µ)
rand()	Returns a random number in the range [0, 1.0)
rand(a,b)	Returns a random number in the range [a, b)
to_unix_timestamp(t)	Converts a time value to a unix timestamp

Adding Activities

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Below is an example of how to add activities with custom ranking:

Retrieving Activities

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Below is an example of how to retrieve activities sorted by custom ranking:

You can only use limit and offset for pagination with custom ranking.

Configuring ranking can be complex. Feel free to reach out to support if you have questions.

Decay & Ranking

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Stream supports a Linear, Exponential, and Gauss decay. For each decay function, we support 4 arguments: Origin, Scale, Offset, and Decay. You can pass either a timedelta string (such as 3d, 4w), or a numeric value.

Parameters

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name	description	default
origin	The best possible value. If the value is equal to the origin the decay function will return 1.	now
scale	Determines how quickly the score drops from 1.0 to the decay value. If the scale is set to "3d" the score will be equal to the decay value after 3 days.	5d
offset	Values below the offset will start to receive a lower score.	0
decay	The score that a value at scale distance from the origin should receive.	0.5
direction	left, right or both. If right is specified only apply the decay for the right part of the graph.	both

You can use s, m, h, d and w to specify seconds, minutes, hours, days and weeks respectively.

The example below defines a simple_gauss with the following params:

scale: 5 days
offset: 1 day
decay: 0.3 day

This means that an activity younger than 1 day (the offset) will return a score of 1. An activity that is exactly 6 days old (offset + scale) will get a score of 0.3 (the decay factor). The full JSON config is shown below:

You can specify defaults for the variables you use. The example above sets popularity to 1 if it's missing from the activity. We highly recommend setting up defaults to prevent errors when retrieving activities without these variables.

Configuring ranking can be complex. Feel free to reach out to support if you have questions!