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| 1 : | gage | 6499 | sub _PGanalyzeGraph_init {} |
| 2 : | |||
| 3 : | ################################################################ | ||
| 4 : | # subroutines | ||
| 5 : | ################################################################ | ||
| 6 : | |||
| 7 : | gage | 6557 | =head1 NAME |
| 8 : | gage | 6499 | |
| 9 : | gage | 6557 | PGanalyzeGraph.pl |
| 10 : | gage | 6499 | |
| 11 : | gage | 6557 | =head1 DESCRIPTION |
| 12 : | |||
| 13 : | These routines support the | ||
| 14 : | analysis of graphical input from students. | ||
| 15 : | |||
| 16 : | =cut | ||
| 17 : | |||
| 18 : | |||
| 19 : | gage | 6499 | =head4 detect_intervals |
| 20 : | |||
| 21 : | gage | 6557 | |
| 22 : | |||
| 23 : | gage | 6499 | input: $pointDisplayString |
| 24 : | gage | 6557 | |
| 25 : | gage | 6499 | return: (\@combined_intervals, \@values) |
| 26 : | @values contains the y values of the function in order | ||
| 27 : | @combined_intervals contains anonymous arrays of the form | ||
| 28 : | [ $slope, $left_x, $right_x] indicating the gradient on that segment. | ||
| 29 : | successive intervals will have different slopes. | ||
| 30 : | |||
| 31 : | |||
| 32 : | =cut | ||
| 33 : | |||
| 34 : | gage | 6557 | |
| 35 : | |||
| 36 : | gage | 6499 | sub detect_intervals { |
| 37 : | my $pointDisplayString = shift; | ||
| 38 : | my @intervals; | ||
| 39 : | my @combined_intervals=(); | ||
| 40 : | my @points; | ||
| 41 : | my @values; | ||
| 42 : | $out_string =''; | ||
| 43 : | return "" unless defined $pointDisplayString and $pointDisplayString =~/\S/; | ||
| 44 : | @pointDisplayLines = split("\n",$pointDisplayString); | ||
| 45 : | #drop first line | ||
| 46 : | #shift @pointDisplayLines; | ||
| 47 : | my ($prev_x, $prev_y, $prev_yp) = (undef); | ||
| 48 : | my $slope; | ||
| 49 : | |||
| 50 : | #first calculate the average gradient on each interval | ||
| 51 : | |||
| 52 : | foreach my $line (@pointDisplayLines) { | ||
| 53 : | chomp($line); | ||
| 54 : | next unless $line =~/\S/; # skip blank lines | ||
| 55 : | ($x,$y,$yp) = split(/\s+/, $line); | ||
| 56 : | |||
| 57 : | if (defined $prev_x) { | ||
| 58 : | $slope = $y - $prev_y; | ||
| 59 : | |||
| 60 : | if ($slope >0) { | ||
| 61 : | $slope_str="increasing"; | ||
| 62 : | } elsif ($slope <0) { | ||
| 63 : | $slope_str="decreasing"; | ||
| 64 : | } else { | ||
| 65 : | $slope_str = "constant"; | ||
| 66 : | } | ||
| 67 : | push @intervals, [$slope_str, $prev_x, $x]; | ||
| 68 : | |||
| 69 : | #TEXT("f is $slope_str on the interval [$prev_x, $x]$BR"); | ||
| 70 : | } | ||
| 71 : | #TEXT("x=$x y = $y yp = $yp $BR"); | ||
| 72 : | push @points, [$x, $y, $yp]; | ||
| 73 : | push @values, $y; | ||
| 74 : | $prev_x =$x; $prev_y=$y; $prev_yp = $yp; | ||
| 75 : | |||
| 76 : | } | ||
| 77 : | my $prev_slope = undef; | ||
| 78 : | my ($left_x, $right_x); | ||
| 79 : | |||
| 80 : | ######## | ||
| 81 : | # Combine adjacent intervals with the same properites | ||
| 82 : | ######## | ||
| 83 : | foreach my $item (@intervals) { | ||
| 84 : | if (defined $prev_slope) { | ||
| 85 : | if ($prev_slope eq $item->[0]) { | ||
| 86 : | $right_x = $item->[2]; | ||
| 87 : | } else { | ||
| 88 : | push @combined_intervals, [$prev_slope, $left_x, $right_x]; | ||
| 89 : | $left_x = $item->[1]; | ||
| 90 : | $right_x = $item->[2]; | ||
| 91 : | } | ||
| 92 : | |||
| 93 : | } else { | ||
| 94 : | $left_x = $item->[1]; | ||
| 95 : | $right_x = $item->[2]; | ||
| 96 : | } | ||
| 97 : | $prev_slope = $item->[0]; | ||
| 98 : | # warn "intervals",join(" ", @combined_intervals); | ||
| 99 : | } | ||
| 100 : | push @combined_intervals, [$prev_slope, $left_x, $right_x]; | ||
| 101 : | |||
| 102 : | (\@combined_intervals, \@values); | ||
| 103 : | } | ||
| 104 : | |||
| 105 : | |||
| 106 : | |||
| 107 : | |||
| 108 : | |||
| 109 : | |||
| 110 : | 1; |
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