Class: WavefrontSparkline

Inherits:
Object
  • Object
show all
Defined in:
lib/wavefront-cli/display/printer/sparkline.rb

Overview

A class to create very simple single-row sparklines of a Wavefront result.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(series) ⇒ WavefrontSparkline

Returns a new instance of WavefrontSparkline.



18
19
20
 
# File 'lib/wavefront-cli/display/printer/sparkline.rb', line 18

def initialize(series)
  @sparkline = ">#{generate_sparkline(series)}<"
end

Instance Attribute Details

#sparkline ⇒ Object (readonly)

Returns the value of attribute sparkline.



16
17
18
 
# File 'lib/wavefront-cli/display/printer/sparkline.rb', line 16

def sparkline
  @sparkline
end

Instance Method Details

#generate_sparkline(data) ⇒ String

Returns the sparkline itself.

Parameters:

  • data (Array) —

    a series of [time, value] data points

Returns:

  • (String) —

    the sparkline itself



49
50
51
52
53
54
55
56
 
# File 'lib/wavefront-cli/display/printer/sparkline.rb', line 49

def generate_sparkline(data)
  values = data.map { |_k, v| v }
  max = values.max || 0
  min = values.min || 0
  v_range = max - min
  values = make_fit(values)
  values.map { |v| sized_block(v - min, v_range) }.join
end

#make_fit(vals) ⇒ Array

A recursive function which repeatedly halves a data series until it fits inside SPARK_WIDTH characters. It does this by merging adjacent pairs and finding the mean. This is crude.

Parameters:

  • vals (Array) —

    a series of values to display

Returns:



38
39
40
41
42
43
44
 
# File 'lib/wavefront-cli/display/printer/sparkline.rb', line 38

def make_fit(vals)
  return vals if vals.size < SPARK_WIDTH

  vals << vals.last if vals.size.odd?
  ret = vals.each_slice(2).with_object([]) { |s, a| a << (s.sum / 2) }
  make_fit(ret)
end

#sized_block(val, range) ⇒ String

Returns the block corresponding to the given value in the given range. The ‘rescue` clause handles occasions when Wavefront returns NaN as a value, or if the range is zero.

Returns:

  • (String) —

    the block corresponding to the given value in the given range. The ‘rescue` clause handles occasions when Wavefront returns NaN as a value, or if the range is zero.



26
27
28
29
30
 
# File 'lib/wavefront-cli/display/printer/sparkline.rb', line 26

def sized_block(val, range)
  BLOCKS[(val / range * (BLOCKS.length - 1)).floor]
rescue StandardError
  BLOCKS.first
end