Line not rendered with data in variable but rendering with array data - ruby-on-rails

Question

I have a method which renders a line graph with Highcharts. The data in the graph is an array in the avg_rates variable, which has these values:
[0.8936e2, 0.8901e2, 0.9015e2, 0.9043e2, 0.8994e2, 0.9105e2, 0, 0, 0, 0, 0, 0]
When I use the variable it doesn't render the line:
f.series(
name: "Average rates",
data: avg_rates
)
When I use the array it does render the line:
f.series(
name: "Average rates",
data: [0.8936e2, 0.8901e2, 0.9015e2, 0.9043e2, 0.8994e2, 0.9105e2, 0, 0, 0, 0, 0, 0]
)
I have no ideay why this is happening? Here is the method in full:
def create_avg_rates_chart(avg_rates)
months = ['jan','feb','mar','apr','mei','jun','jul','aug','sep','okt','nov', 'dec']
min = avg_rates[0] - 5
max = avg_rates[0] + 5
avg_rates_chart = LazyHighCharts::HighChart.new('graph') do |f|
f.chart(type: 'line', height: '150', width: '1000')
f.pane(size: '100%')
f.colors(['#0092C9'])
f.xAxis(
categories: months.map{ |m| [m] },
labels: {
style: { "fontSize": "12px" }
}
)
f.yAxis(
title: {
text: 0
},
min: min,
max: max
)
f.plotOptions(
line: {
dataLabels: {
enabled: true,
padding: 10
},
enableMouseTracking: false,
lineWidth: 4,
marker: {
radius: 5
}
}
)
f.series(
name: "Average rates",
data: avg_rates
)
f.legend(enabled: false)
end
end

Answer 1

This most likely happens because when you copied the contents from the array variable you don't copy the actual object but just the console representation (aka the result of #inspect).
The array avg_rates most likely happens to contain BigDecimals:
# avg_rates comes in from outside the function, the line below is a mock.
avg_rates = %w[89.36 89.01 90.15 90.43 89.94 91.05 0 0 0 0 0 0].map(&:to_d)
These values are represented in the console using the #inspect method and produce the following visual output:
#=> [0.8936e2, 0.8901e2, 0.9015e2, 0.9043e2, 0.8994e2, 0.9105e2, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
This visual output is also perfectly valid Ruby code. However if you type 0.8936e2 into the console you'll instantiate a Float and not a BigDecimal. This can be seen if you look at the return value of just entering the the representation of the array:
avg_rates_repr = [0.8936e2, 0.8901e2, 0.9015e2, 0.9043e2, 0.8994e2, 0.9105e2, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
#=> [89.36, 89.01, 90.15, 90.43, 89.94, 91.05, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
avg_rates.map(&:class).uniq
#=> [BigDecimal]
avg_rates_repr.map(&:class).uniq
#=> [Float]
As you said the graph doesn't render when using the avg_rates variable, but does with the copying the representation. This means that LazyHighCharts::HighChart doesn't accept BigDecimals but does accept Floats. So your solution should be to convert the values to Floats before passing them to the :data option of #series.
data: avg_rates.map(&:to_f)