(Rails) Creating multi-dimensional hashes/arrays from a data set...?

Question

Hi All,

I'm having a bit of an issue wrapping my head around something. I'm currently using a hacked version of Gruff in order to accommodate "Scatter Plots". That said, the data is entered in the form of:

 g.data("Person1",[12,32,34,55,23],[323,43,23,43,22])

...where the first item is the ENTITY, the second item is X-COORDs, and the third item is Y-COORDs.

I currently have a recordset of items from a table with the columns: POINT, VALUE, TIMESTAMP. Due to the "complex" calculations involved I must grab everything using a single query or risk way too much DB activity. That said, I have a list of items for which I need to dynamically collect all data from the recordset into a hash (or array of arrays) for the creation of the data items. I was thinking something like the following:

 @h={}

 e = Events.find_by_sql(my_query)
 e.each do |event|
      @h["#{event.Point}"][x] = event.timestamp
      @h["#{event.Point}"][y] = event.value
 end

Obviously that's not the correct syntax, but that's where my brain is going. Could someone clean this up for me or suggest a more appropriate mechanism by which to accomplish this? Basically the main goal is to keep data for each pointname grouped (but remember the recordset has them all).

Much appreciated.

EDIT 1

g = Gruff::Scatter.new("600x350")
g.title = self.name

e = Event.find_by_sql(@sql)

h ={}

e.each do |event|
  h[event.Point.to_s] ||= {}
  h[event.Point.to_s].merge!({event.Timestamp.to_i,event.Value})
end

h.each do |p|

  logger.info p[1].values.inspect

  g.data(p[0],p[1].keys,p[1].values)
end

g.write(@chart_file)

Answer 1

First off, don't use string interpolation when a simple o.to_s will do.

@h[event.Point.to_s]

The structure of your data is not clear from the description. I think you mean that there 1) there are events with Point names 2) each event has a time and a value 3) you want to manipulate a collection of events.

A hash is a fine choice for the problem.