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Re^3: Parsing an SQL table using an array of hashes?

by poj (Priest)
on Jun 29, 2013 at 06:53 UTC ( #1041406=note: print w/ replies, xml ) Need Help??


in reply to Re^2: Parsing an SQL table using an array of hashes?
in thread Parsing an SQL table using an array of hashes?

If you are likely to plot across years or over a period of say the last x months, then it may be convenient to convert your year and months into a 'period number'. Then you can store the data in a hash like this ;

$data{'category'}[period]

Storing a string of month/year in another array using the same period numbers as the index makes it easy to build the first record of your plot data.

Here is an example of what I mean with your data expanded into 2014.

#perl use strict; use GD::Graph; use GD::Graph::bars; my $YEAR1 = 2013; my @period=(); my %y_data=(); my @x_legend=(); # stroe data while (<DATA>){ chomp; my ($m,$y,$cat,$n) = split ',',$_; # convert year/month to period number my $pd = ym_to_pd($y,$m); $period[$pd] = "$m/$y"; $y_data{$cat}[$pd] = $n; } # graph data my @y_plotdata; push @y_plotdata,[@period]; for my $cat (sort keys %y_data){ push @x_legend,$cat; push @y_plotdata,[@{$y_data{$cat}}]; } # create graph my $my_graph = GD::Graph::bars->new(800,600); $my_graph->set( x_label => 'X Label', y_label => 'Y label', title => 'Title', ); $my_graph->set_legend(@x_legend); my $img = $my_graph->plot(\@y_plotdata) or die $my_graph->error; # save image open(IMG,'>','plot.gif') or die "$!"; binmode IMG; print IMG $img->png; close IMG; # convert year,month to period sub ym_to_pd { my ($yr,$mth) = @_; return ($yr - $YEAR1) * 12 + $mth; } # convert period to year.month sub pd_to_ym { my $ix = shift; my $yr = int(($ix-1)/12)+$YEAR1; my $mth = $ix-12*($yr-$YEAR1); return ($yr,$mth); } #test_periods(); sub test_periods { for my $y (2013..2015){ for my $m (1..12){ my $pd = ym_to_pd($y,$m); my ($yr,$mth) = pd_to_ym($pd); print "$y $m => $pd => $yr $mth\n"; } } } __DATA__ 3,2013,Address,1 2,2013,Equipment,13 3,2013,Equipment,18 4,2013,Equipment,17 5,2013,Equipment,8 3,2013,Database Reconciliation,3 5,2013,Database Reconciliation,3 2,2013,Design/Process,123 3,2013,Design/Process,74 4,2013,Design/Process,42 5,2013,Design/Process,30 1,2014,Design/Process,30
poj


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Re^4: Parsing an SQL table using an array of hashes?
by chareTX (Initiate) on Jul 01, 2013 at 00:33 UTC
    Thank you very much -- this was very helpful. Two questions:

    1. Can you explain this line for me please? I am just not sure I get it.

     push @y_plotdata,[@{$y_data{$cat}}];

    2. I need to do the same thing, but reversed -- instead of category being the legend and dates on the x-axis, I need to do the categories on the a-axis, and the months in the legend.

    I haven't started experimenting with it yet, but I wanted to say thanks for your help.

      [@{$y_data{$cat}}] is a ref to a copy of the data for one $cat.

      It is equivalent to [ $y_data{$cat}[0],$y_data{$cat}[1],$y_data{$cat}[2],etc ]

      For a plot of all periods this would work equally as well

      push @y_plotdata,$y_data{$cat};
      poj
Re^4: Parsing an SQL table using an array of hashes?
by chareTX (Initiate) on Jul 02, 2013 at 19:50 UTC

    So, thanks for the excellent example. But, I now need to do it the other way. instead of having the categories in the legend, i need the categories on the x-axis and the periods in the legend. I think I can do that with the code you provided, but honestly, we are getting to the edge of my PERL knowledge.

      Little more complicated because you have to define an order for the categories, I have chosen a alphabetic sort.
      #perl use strict; use GD::Graph; use GD::Graph::bars; my $YEAR1 = 2013; my @period=(); my %y_data=(); my @x_legend=(); my %x_data=(); # store data while (<DATA>){ chomp; my ($m,$y,$cat,$n) = split ',',$_; # convert year/month to period number my $pd = ym_to_pd($y,$m); $period[$pd] = "$m/$y"; $y_data{$cat}[$pd] = $n; ++$x_data{$pd}; } # graph data my @y_plotdata; my @categories = sort keys %y_data; push @y_plotdata,[@categories]; for my $pd (sort {$a<=>$b} keys %x_data){ push @x_legend,$period[$pd]; my @y_data=(); for my $cat (@categories){ push @y_data,$y_data{$cat}[$pd]; } push @y_plotdata,[ @y_data ]; } # create graph my $my_graph = GD::Graph::bars->new(800,600); $my_graph->set( x_label => 'X Label', y_label => 'Y label', title => 'Title', ); $my_graph->set_legend(@x_legend); my $img = $my_graph->plot(\@y_plotdata) or die $my_graph->error; # save image open(IMG,'>','plot.gif') or die "$!"; binmode IMG; print IMG $img->png; close IMG; # convert year,month to period sub ym_to_pd { my ($yr,$mth) = @_; return ($yr - $YEAR1) * 12 + $mth; } # convert period to year.month sub pd_to_ym { my $ix = shift; my $yr = int(($ix-1)/12)+$YEAR1; my $mth = $ix-12*($yr-$YEAR1); return ($yr,$mth); } #test_periods(); sub test_periods { for my $y (2013..2015){ for my $m (1..12){ my $pd = ym_to_pd($y,$m); my ($yr,$mth) = pd_to_ym($pd); print "$y $m => $pd => $yr $mth\n"; } } } __DATA__ 3,2013,Address,1 2,2013,Equipment,13 3,2013,Equipment,18 4,2013,Equipment,17 5,2013,Equipment,8 3,2013,Database Reconciliation,3 5,2013,Database Reconciliation,3 2,2013,Design/Process,123 3,2013,Design/Process,74 4,2013,Design/Process,42 5,2013,Design/Process,30 1,2014,Design/Process,30
      Updated : period loop uses new %x_data :
      for my $pd (sort {$a<=>$b} keys %x_data){ push @x_legend,$period[$pd];
      poj

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