Differential D20454 Diff 48950 src/applications/fact/chart/PhabricatorAccumulateChartFunction.php

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src/applications/fact/chart/PhabricatorAccumulateChartFunction.php

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				<?php

				final class PhabricatorAccumulateChartFunction
				extends PhabricatorChartFunction {

				const FUNCTIONKEY = 'accumulate';

				protected function newArguments() {
				return array(
				$this->newArgument()
				->setName('x')
				->setType('function'),
				);
				}

				public function getDomain() {
				return $this->getArgument('x')->getDomain();
				}

				public function newInputValues(PhabricatorChartDataQuery $query) {
				return $this->getArgument('x')->newInputValues($query);
				}

				public function evaluateFunction(array $xv) {
				// First, we're going to accumulate the underlying function. Then
				// we'll map the inputs through the accumulation.

				$datasource = $this->getArgument('x');

				// Use an unconstrained query to pull all the data from the underlying
				// source. We need to accumulate data since the beginning of time to
				// figure out the right Y-intercept -- otherwise, we'll always start at
				// "0" wherever our domain begins.
				$empty_query = new PhabricatorChartDataQuery();

				$datasource_xv = $datasource->newInputValues($empty_query);
				if (!$datasource_xv) {
				// TODO: Maybe this should just be an error?
				$datasource_xv = $xv;
				epriestleyAuthorUnsubmitted Done Inline Actions This is when you `x \| accumulate` and numerically approximate the integral of some pure math function. It "works" (produces a meaningful -- but possibly inaccurate -- integral using crude numerical methods) and letting you do this means I don't have to classify functions anymore, so I'm just allowing this for now. If this is too confusing we could stop it later, but I don't think users are going to see this stuff. epriestley: This is when you `x \| accumulate` and numerically approximate the integral of some pure math…
				}

				$yv = $datasource->evaluateFunction($datasource_xv);

				$map = array_combine($datasource_xv, $yv);

				$accumulator = 0;
				foreach ($map as $x => $y) {
				$accumulator += $y;
				$map[$x] = $accumulator;
				}

				// The value of "accumulate(x)" is the largest datapoint in the map which
				// is no larger than "x".
				amckinleyUnsubmitted Not Done Inline Actions "is the largest" amckinley: "is the largest"

				$map_x = array_keys($map);
				$idx = -1;
				$max = count($map_x) - 1;

				$yv = array();

				$value = 0;
				foreach ($xv as $x) {
				// While the next "x" we need to evaluate the function at lies to the
				// right of the next datapoint, move the current datapoint forward until
				// we're at the rightmost datapoint which is not larger than "x".
				while ($idx < $max) {
				if ($map_x[$idx + 1] > $x) {
				break;
				}

				$idx++;
				$value = $map[$map_x[$idx]];
				}

				$yv[] = $value;
				}

				return $yv;
				}

				}