"I wrote this code to calculate the range of colors between 2 colors to plot using the range from color_a to color_b..." I have changed the code and repackaged it, but the idea is the same. Given 2 colors and number of data sets, computes an array of colors that make up a gradient between the two provided colors, for use with SetDataColors(). Provides the following functions: $colors = color_range($color_a, $color_b, $n_intervals) Returns a color array for SetDataColors. $n = count_data_sets($data, $data_type) Counts the number of data sets in a data array. This can be used to provide $n_intervals in color_range(). */ /* Fill a color map with a gradient step between two colors. Arguments: $color_a : Starting color for the gradient. Array of (r, g, b) $color_b : Ending color for the gradient. Array of (r, g, b) $n_steps : Total number of color steps, including color_a and color_b. Returns: A color map array with n_steps colors in the form $colors[i][3], suitable for SetDataColors(). Notes: You may use the PHPlot internal function $plot->SetRGBColor($color) to convert a color name or #rrggbb notation into the required array of 3 values (r, g, b) for color_a and color_b. */ function color_range($color_a, $color_b, $n_steps) { if ($n_steps < 2) $n_steps = 2; $nc = $n_steps - 1; # Note: $delta[] and $current[] are kept as floats. $colors is integers. for ($i = 0; $i < 3; $i++) $delta[$i] = ($color_b[$i] - $color_a[$i]) / $nc; $current = $color_a; for ($col = 0; $col < $nc; $col++) { for ($i = 0; $i < 3; $i++) { $colors[$col][$i] = (int)$current[$i]; $current[$i] += $delta[$i]; } } $colors[$nc] = $color_b; # Make sure the last color is exact. return $colors; } /* Determine the number of data sets (plot lines, bars per group, pie segments, etc.) contained in a data array. This can be used to determine n_steps for $color_range. Arguments: $data : PHPlot data array $data_type : PHPlot data type, describing $data. (e.g. 'data-data') Returns: The number of data sets in the data array. Notes: This has to scan the entire data array. Don't use this unless you really don't have a better way to determine the number of data sets. This does NOT require that the data array be integer indexed. */ function count_data_sets($data, $data_type) { if ($data_type == 'text-data-single') return count($data); # Pie chart, 1 segment per record # Get the longest data record: $max_row = 0; foreach ($data as $row) if (($n = count($row)) > $max_row) $max_row = $n; if ($data_type == 'text-data') return ($max_row - 1); # Each record is (label Y1 Y2...) if ($data_type == 'data-data') return ($max_row - 2); # Each record is (label X Y1 Y2...) if ($data_type == 'data-data-error') return (($max_row - 2) / 3); # Each record is (label X Y1 Y1+ Y1-...) # Not a recognized data type... Just return something sane. return $max_row; }