added file downloads but **NOT TESTED**

app/controllers/db_streams_controller.rb

@@ -15,6 +15,14 @@ class DbStreamsController < ApplicationController
   end
 
   def data
+    @service = BuildDataset.new
+    @service.run(@db_stream,params[:start_time].to_i,params[:end_time].to_i)
+    unless @service.success?
+      head :unprocessable_entity
+      return
+    end
+    @data = @service.data
+    @legend = @service.legend
     headers["Content-Disposition"] = "attachment; filename='#{@db_stream.name}.txt'"
     render :layout=>false, :content_type => "text/plain"
   end

app/services/data/build_dataset.rb

+# frozen_string_literal: true
+
+# Creates a dataset array from the given stream
+# at the highest resolution allowed by the db
+#
+class BuildDataset
+  include ServiceStatus
+  attr_reader :data, :legend
+
+  def initialize
+    super()
+    @data = [] # [[ts, val1, val2, val3, ...],
+               # [ts, val1, val2, val3, ...]]
+    @legend = {
+      start_time: '',
+      end_time: '',
+      num_rows: '',
+      decimation_factor: 1,
+      columns: [], # [{index: 1, name: 'time', units: 'us'},...]
+      notes: ''
+    }
+  end
+
+  # fill @data with values from db_stream
+  # and populate @legend
+  def run(db_stream, start_time, end_time)
+    adapter = DbAdapter.new(db_stream.db.url)
+    data_service = LoadStreamData.new(adapter)
+    data_service.run(db_stream, start_time, end_time)
+    unless data_service.success?
+      add_error("unable to retrieve data for #{stream.path}")
+      return self
+    end
+    @data = _build_dataset(data_service.data)
+    @legend[:columns]           = _build_legend_columns(data_service.data, db_stream)
+    @legend[:start_time]        = start_time
+    @legend[:end_time]          = end_time
+    @legend[:decimation_factor] = data_service.decimation_factor
+    @legend[:num_rows]          = @data.length
+    if(@data[0].length!=db_stream.db_elements.length+1)
+      @legend[:notes] = 'some elements omitted due to insufficient decimation'
+    end
+    self
+  end
+
+  def _build_dataset(stream_data)
+    #can only build a dataset if data is actually present (raw or decimated)
+    valid_columns = stream_data.select{|d| d[:type]!='interval'}
+    return [] if(valid_columns.empty?)
+
+    cleaned_columns = valid_columns.map do |element_data|
+      element_data[:values].select{|row| row!=nil}
+    end
+    data_columns = []
+    #first column is the timestamp
+    data_columns << cleaned_columns.first.transpose[0]
+    #add element data by column
+    cleaned_columns.each do |data|
+        data_columns << data.transpose[1]
+    end
+    data_columns.transpose
+  end
+
+  def _build_legend_columns(stream_data, db_stream)
+    legend_columns = [{index: 1, name: 'time', units: 'us'}]
+    legend_index=2 #1 is for timestamp
+    stream_data.each do |d|
+      next if d[:type]=='interval'
+      element = db_stream.db_elements.find_by_id(d[:id])
+      legend_columns<<{
+        index: legend_index,
+        name: element.name,
+        units: element.units.blank? ? 'no units': element.units
+      }
+      legend_index+=1
+    end
+    legend_columns
+  end
+end

app/services/data/load_stream_data.rb

@@ -3,13 +3,14 @@
 # Loads stream data over specified interval
 class LoadStreamData
   include ServiceStatus
-  attr_reader :data, :data_type
+  attr_reader :data, :data_type, :decimation_factor
 
   def initialize(db_adapter)
     super()
     @db_adapter = db_adapter
     @data = []
     @data_type = 'unset' # interval, raw, decimated
+    @decimation_factor = 1
   end
 
   # load data at or below the resolution of the
@@ -19,12 +20,16 @@ class LoadStreamData
   # data_type: raw
   # data:
   #   [{id: element_id, type: raw values: [[ts,y],[ts,y],nil,[ts,y]]},...]
-  # data_type: interval
-  # data:
-  #   [{id: element_id, type: raw, values: [[start,0],[end,0],nil,...]}]
+  #
   # data_type: decimated
+  # event data:
+  #   [{id: element_id, type: decimated, values: [[start,0],[end,0],nil,...]}]
+  # continuous or discrete data:
+  #   [{id: element_id, type: decimated, values: [[ts,y,ymin,ymax],[ts,y,ymin,ymax],nil,...]}]
+  #
+  # data_type: interval
   # data:
-  #   [{id: element_id, type: raw, values: [[ts,y,ymin,ymax],[ts,y,ymin,ymax],nil,...]}]
+  #   [{id: element_id, type: decimated, values: [[start,0],[end,0],nil,...]}]
   #
   def run(db_stream, start_time, end_time)
     resolution = db_stream.db.max_points_per_plot
@@ -45,7 +50,8 @@ class LoadStreamData
       @data = __build_interval_data(elements, resp)
       return self
     end
-    # request is plottable, see if we can get the raw (level 1) data
+    # request is plottable, see if we can get the data
+    @decimation_factor = plottable_decim.level
     path = __build_path(db_stream, plottable_decim.level)
     resp = @db_adapter.get_data(path, start_time, end_time)
     if resp.nil?

app/views/db_streams/data.csv.erb

@@ -4,26 +4,29 @@
 # Source: <%=@nilm.name%> <%unless @nilm.description.blank?%>(<%=@nilm.description%>)<%end%>
 #
 #
-# start:      --
-# end:        --
-# total time: --
-# total rows: --
+# start:             <%=Time.at(@legend[:start_time]/1e6)%>
+# end:               <%=Time.at(@legend[:end_time]/1e6)%>
+# total time:        <%=distance_of_time_in_words(@legend[:end_time]/1e6-@legend[:start_time]/1e6)%>
+# total rows:        <%=@legend[:num_rows]%>
+# decimation factor: <%=@legend[:decimation_factor]%>
 #
-#The raw data file can be retrieved at the following URL:
-# <%=@db.url%>/stream/extract?path=<%=@db_stream.path%>&start=?&end=?
+# this file can be loaded directly into MATLAB
 #
-# to import in matlab run:
-# 	nilm = importdata('thisfilename.txt')
+# 	dataset = importdata('thisfilename.csv')
 #
-# nilm.textdata: this help text
-# nilm.data:     the data
+# dataset.textdata: this help text
+# dataset.data:     the data
 #
-# The data has <%= @db_stream.db_elements.count+1 %> columns with the following format:
+# raw data can be accessed using nilmtool, run:
+# nilmtool -u <%=@db.url%> extract -s @<%=@legend[:start_time]%> -e @<%=@legend[:end_time]%> <%=@db_stream.path%>
 #
-#  Column 1: Timestamp (microseconds)
-	<% col = 2%>
-	<%@db_stream.db_elements.each do |element|%>
-#  Column <%=col%>: <%=element.name%> (<%=element.units%>)
-	<%col+=1%>
-	<%end%>
+# <%=@legend[:notes]%>
+#  ----------- LEGEND ---------------
+<%@legend[:columns].each do |col|%>
+# Column <%=col[:index]%>: <%=col[:name]%> (<%=col[:units]%>)
+<%end%>
+# -----------------------------------
 #
+<% @data.each do |row|%>
+<%= row.join(", ")%>
+<%end%>