# Replace Value Functions

# Overview

This document describes fields and functions, which can be referenced in the replace-value setting to replace or remove values of the current series.

The replace-value setting is specified in the [series] section.

[series]
  metric = cpu_busy
  entity = nurswgvml007
  replace-value = Math.log(value)

# Fields

Field	Description
value	Value of the series at the current timestamp.
previousValue	Value at the previous timestamp.
time	Current timestamp measured as Unix time in milliseconds.
previousTime	Previous timestamp measured as Unix time in milliseconds.

# Examples

replace-value = value/60

replace-value = Math.log(value)

replace-value = value/Math.pow(2, 20)

replace-value = -value

replace-value = Math.max(0, value)

replace-value = value <= 0 ? null : value

replace-value = time < new Date('2018-12-15T00:00:00Z').getTime() ? null : value

replace-value = time > 1519862400000 ? null : value

replace-value = (time < 1455889800000 || time > 1455890400000) ? null : value

replace-value = ( time < new Date('2016-02-19T13:50:00Z').getTime() || time > new Date('2016-02-19T14:00:00Z').getTime() ) ? value : null

replace-value = value - previousValue

replace-value = value/previousValue

replace-value = (value/previousValue - 1) * 100

replace-value = var v = value, pv = previousValue, t = time, pt = previousTime; return (pv === null) ? null : (v - pv)/(t - pt);

# Window Functions

Define a custom JavaScript function in the window object using the script / endscript section in the configuration text.

script
  window.checkRange = function (val) {
     if (val > 100) {
       return null;
     }
     return val;
  };
endscript

The custom function can be accessed in the replace-value setting by referencing it by name.

replace-value = return checkRange(value);

Functions in the window scope can be invoked in other settings that support functions, for example, in the format setting.