diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -2649,6 +2649,7 @@
     'PhabricatorChangeParserTestCase' => 'applications/repository/worker/__tests__/PhabricatorChangeParserTestCase.php',
     'PhabricatorChangesetCachePurger' => 'applications/cache/purger/PhabricatorChangesetCachePurger.php',
     'PhabricatorChangesetResponse' => 'infrastructure/diff/PhabricatorChangesetResponse.php',
+    'PhabricatorChartFunction' => 'applications/fact/function/PhabricatorChartFunction.php',
     'PhabricatorChatLogApplication' => 'applications/chatlog/application/PhabricatorChatLogApplication.php',
     'PhabricatorChatLogChannel' => 'applications/chatlog/storage/PhabricatorChatLogChannel.php',
     'PhabricatorChatLogChannelListController' => 'applications/chatlog/controller/PhabricatorChatLogChannelListController.php',
@@ -3203,6 +3204,7 @@
     'PhabricatorFactApplication' => 'applications/fact/application/PhabricatorFactApplication.php',
     'PhabricatorFactChart' => 'applications/fact/storage/PhabricatorFactChart.php',
     'PhabricatorFactChartController' => 'applications/fact/controller/PhabricatorFactChartController.php',
+    'PhabricatorFactChartFunction' => 'applications/fact/function/PhabricatorFactChartFunction.php',
     'PhabricatorFactController' => 'applications/fact/controller/PhabricatorFactController.php',
     'PhabricatorFactCursor' => 'applications/fact/storage/PhabricatorFactCursor.php',
     'PhabricatorFactDAO' => 'applications/fact/storage/PhabricatorFactDAO.php',
@@ -8619,6 +8621,7 @@
     'PhabricatorChangeParserTestCase' => 'PhabricatorWorkingCopyTestCase',
     'PhabricatorChangesetCachePurger' => 'PhabricatorCachePurger',
     'PhabricatorChangesetResponse' => 'AphrontProxyResponse',
+    'PhabricatorChartFunction' => 'Phobject',
     'PhabricatorChatLogApplication' => 'PhabricatorApplication',
     'PhabricatorChatLogChannel' => array(
       'PhabricatorChatLogDAO',
@@ -9235,6 +9238,7 @@
       'PhabricatorPolicyInterface',
     ),
     'PhabricatorFactChartController' => 'PhabricatorFactController',
+    'PhabricatorFactChartFunction' => 'PhabricatorChartFunction',
     'PhabricatorFactController' => 'PhabricatorController',
     'PhabricatorFactCursor' => 'PhabricatorFactDAO',
     'PhabricatorFactDAO' => 'PhabricatorLiskDAO',
diff --git a/src/applications/fact/controller/PhabricatorFactChartController.php b/src/applications/fact/controller/PhabricatorFactChartController.php
--- a/src/applications/fact/controller/PhabricatorFactChartController.php
+++ b/src/applications/fact/controller/PhabricatorFactChartController.php
@@ -12,81 +12,38 @@
     $is_chart_mode = ($mode === 'chart');
     $is_draw_mode = ($mode === 'draw');
 
-    $series = $request->getStr('y1');
+    $functions = array();
 
-    $facts = PhabricatorFact::getAllFacts();
-    $fact = idx($facts, $series);
+    $functions[] = id(new PhabricatorFactChartFunction())
+      ->setArguments(array('tasks.count.create'));
 
-    if (!$fact) {
-      return new Aphront404Response();
-    }
-
-    $key_id = id(new PhabricatorFactKeyDimension())
-      ->newDimensionID($fact->getKey());
-    if (!$key_id) {
-      return new Aphront404Response();
-    }
+    $functions[] = id(new PhabricatorFactChartFunction())
+      ->setArguments(array('tasks.open-count.create'));
 
     if ($is_chart_mode) {
       return $this->newChartResponse();
     }
 
-    $table = $fact->newDatapoint();
-    $conn_r = $table->establishConnection('r');
-    $table_name = $table->getTableName();
-
-    $data = queryfx_all(
-      $conn_r,
-      'SELECT value, epoch FROM %T WHERE keyID = %d ORDER BY epoch ASC',
-      $table_name,
-      $key_id);
-
-    $points = array();
-    $sum = 0;
-    foreach ($data as $key => $row) {
-      $sum += (int)$row['value'];
-      $points[(int)$row['epoch']] = $sum;
-    }
+    $datasets = array();
+    foreach ($functions as $function) {
+      $function->loadData();
 
-    if (!$points) {
-      throw new Exception('No data to show!');
-    }
+      $points = $function->getDatapoints(2000);
 
-    // Limit amount of data passed to browser.
-    $count = count($points);
-    $limit = 2000;
-    if ($count > $limit) {
-      $i = 0;
-      $every = ceil($count / $limit);
-      foreach ($points as $epoch => $sum) {
-        $i++;
-        if ($i % $every && $i != $count) {
-          unset($points[$epoch]);
-        }
-      }
-    }
-
-    $datasets = array();
+      $x = array();
+      $y = array();
 
-    $datasets[] = array(
-      'x' => array_keys($points),
-      'y' => array_values($points),
-      'color' => '#ff0000',
-    );
+      foreach ($points as $point) {
+        $x[] = $point['x'];
+        $y[] = $point['y'];
+      }
 
-    // Add a dummy "y = x" dataset to prove we can draw multiple datasets.
-    $x_min = min(array_keys($points));
-    $x_max = max(array_keys($points));
-    $x_range = ($x_max - $x_min) / 4;
-    $linear = array();
-    foreach ($points as $x => $y) {
-      $linear[$x] = round(count($points) * (($x - $x_min) / $x_range));
+      $datasets[] = array(
+        'x' => $x,
+        'y' => $y,
+        'color' => '#ff00ff',
+      );
     }
-    $datasets[] = array(
-      'x' => array_keys($linear),
-      'y' => array_values($linear),
-      'color' => '#0000ff',
-    );
 
     $y_min = 0;
     $y_max = 0;
diff --git a/src/applications/fact/function/PhabricatorChartFunction.php b/src/applications/fact/function/PhabricatorChartFunction.php
new file mode 100644
--- /dev/null
+++ b/src/applications/fact/function/PhabricatorChartFunction.php
@@ -0,0 +1,24 @@
+<?php
+
+abstract class PhabricatorChartFunction
+  extends Phobject {
+
+  final public function getFunctionKey() {
+    return $this->getPhobjectClassConstant('FUNCTIONKEY', 32);
+  }
+
+  final public static function getAllFunctions() {
+    return id(new PhutilClassMapQuery())
+      ->setAncestorClass(__CLASS__)
+      ->setUniqueMethod('getFunctionKey')
+      ->execute();
+  }
+
+  final public function setArguments(array $arguments) {
+    $this->newArguments($arguments);
+    return $this;
+  }
+
+  abstract protected function newArguments(array $arguments);
+
+}
diff --git a/src/applications/fact/function/PhabricatorFactChartFunction.php b/src/applications/fact/function/PhabricatorFactChartFunction.php
new file mode 100644
--- /dev/null
+++ b/src/applications/fact/function/PhabricatorFactChartFunction.php
@@ -0,0 +1,102 @@
+<?php
+
+final class PhabricatorFactChartFunction
+  extends PhabricatorChartFunction {
+
+  const FUNCTIONKEY = 'fact';
+
+  private $factKey;
+  private $fact;
+  private $datapoints;
+
+  protected function newArguments(array $arguments) {
+    if (count($arguments) !== 1) {
+      throw new Exception(
+        pht(
+          'Chart function "fact(...)" expects one argument, got %s. '.
+          'Pass the key for a fact.',
+          count($arguments)));
+    }
+
+    if (!is_string($arguments[0])) {
+      throw new Exception(
+        pht(
+          'First argument for "fact(...)" is invalid: expected string, '.
+          'got %s.',
+          phutil_describe_type($arguments[0])));
+    }
+
+    $facts = PhabricatorFact::getAllFacts();
+    $fact = idx($facts, $arguments[0]);
+
+    if (!$fact) {
+      throw new Exception(
+        pht(
+          'Argument to "fact(...)" is invalid: "%s" is not a known fact '.
+          'key.',
+          $arguments[0]));
+    }
+
+    $this->factKey = $arguments[0];
+    $this->fact = $fact;
+  }
+
+  public function loadData() {
+    $fact = $this->fact;
+
+    $key_id = id(new PhabricatorFactKeyDimension())
+      ->newDimensionID($fact->getKey());
+    if (!$key_id) {
+      return;
+    }
+
+    $table = $fact->newDatapoint();
+    $conn = $table->establishConnection('r');
+    $table_name = $table->getTableName();
+
+    $data = queryfx_all(
+      $conn,
+      'SELECT value, epoch FROM %T WHERE keyID = %d ORDER BY epoch ASC',
+      $table_name,
+      $key_id);
+    if (!$data) {
+      return;
+    }
+
+    $points = array();
+
+    $sum = 0;
+    foreach ($data as $key => $row) {
+      $sum += (int)$row['value'];
+      $points[] = array(
+        'x' => (int)$row['epoch'],
+        'y' => $sum,
+      );
+    }
+
+    $this->datapoints = $points;
+  }
+
+  public function getDatapoints($limit) {
+    $points = $this->datapoints;
+    if (!$points) {
+      return array();
+    }
+
+    // If we have too many data points, throw away some of the data.
+    $count = count($points);
+    if ($count > $limit) {
+      $ii = 0;
+      $every = ceil($count / $limit);
+      foreach ($points as $key => $point) {
+        $ii++;
+        if (($ii % $every) && ($ii != $count)) {
+          unset($points[$key]);
+        }
+      }
+    }
+
+    return $points;
+  }
+
+}