jenks.php 24.1 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626
<?php
/**
  * Copyright (c) 2012 David Drake
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *    http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

/**
  * Jenk's Natural Breaks Classification Scheme with Google Charts API
  *
  * Some of this code is a translation / reworking of a script from French to English. The source script 
  * was written by Dominique Ollivier, Luc Guillemot and Dominique Pelage and can be found here: 
  * http://www.forumsig.org/showthread.php?t=22055
  *
  * Many bug fixes and significant improvements as well as the tie in to the Google Charts API were done by
  * David Drake.
  */

/** 
  * This function will determine which classNumber a particular value rank/key falls in 
  *
  * @param int $valueRank - the rank of value in the sorted list of values
  * @param int $numberOfClasses - the number of classes desired
  * @param array $numberOfElementsPerClassArray - the array of classes holding the number of elements per class
  */
function determineClass ($valueRank, $numberOfClasses, $numberOfElementsPerClassArray) {
	$minimum = 0;
	$maximum = $numberOfElementsPerClassArray[0] - 1;
	for ($ii = 0; $ii < $numberOfClasses; $ii++) {
		if ($valueRank >= $minimum && $valueRank <= $maximum) {
			$classNumber = $ii;
		}
	
		$minimum = $minimum + $numberOfElementsPerClassArray[$ii];
		$maximum = $minimum + $numberOfElementsPerClassArray[$ii + 1] - 1;
	}
	
	return $classNumber;
}

/**
  * This function will determine the maximum values for the classes
  *
  * @param array $values - the values
  * @param array $classes - the classes 
  */
function getClassMaximums ($values, $classes) {
	$numberValues = count($values);
	$numberOfClasses = count($classes);
	$maximumValues = array();

	// Make sure our values are sorted
	array_multisort($values);

	$valueIndex = 0;
	for ($classNumber = 0; $classNumber < $numberOfClasses; $classNumber++) {
		$maximumValues[$classNumber] = $values[$valueIndex];
		$valueIndex = $valueIndex + $classes[$classNumber];
	}

	$maximumValues[$numberOfClasses] = $values[$numberValues - 1];

	return $maximumValues;
}

/**
  * This function will determine the number of values that belong in each class
  *
  * @param array $values - the values
  * @param array $maximumValues - the maximum values of each class
  */
function getNumberOfValuesPerClass ($values, $maximumValues) {
	$numberOfClasses = count($maximumValues) - 1;
	$numberOfValues = count($values);
	$class = array();

	// Make sure our values are sorted
	array_multisort($values);

	$firstValueOfClass = 0;

	for ($classNumber = 1; $classNumber < $numberOfClasses; $classNumber++) {
		$crossIndex = 0;
		while ($values[$crossIndex] < $maximumValues[$classNumber] && $crossIndex < $numberOfValues) {
			$crossIndex++;
		}
		$lastClassIndex = $crossIndex - 1;

		$class[$classNumber - 1] = $lastClassIndex - $firstValueOfClass + 1;
		$firstValueOfClass = $lastClassIndex + 1;
	}

	$class[$classNumber - 1] = $numberOfValues - $firstValueOfClass;

	return $class;
}	

/**
  * Calculates an average of the values in an array
  *
  * @param array $values - the array of values you want an average calculated for
  */
function calculateAverage ($values) {
	if (!is_array($values) || count($values) == 0) {
		return 0;
	}
	return array_sum($values) / count($values);
}

/**
  * The Jenks Algorithm
  *
  * This function will determine the optimal natural breaks for a set of values given a number of classes. It will return
  * an array of classes with the number of elements for each class.
  *
  * @param int $numberOfClasses - the number of classes you want
  * @param array $values - the values you are working with 
  */
function getJenksClasses ($numberOfClasses, $values) {
	// Make sure our values are sorted 
	array_multisort($values);

	// Determine the number of values
	$numberOfValues = count($values);

	// If we have the same number of unique values as classes 
	if (count(array_unique($values)) == $numberOfClasses) {
		// Then we can just count up the number of values in each of the classes and we are finished
		$classes = array_values(array_count_values($values));
		return getClassMaximums($values, $classes);
	}
	
	// We need a starting point for Jenks. Let's start with a simple quantile split
	$classSize = floor($numberOfValues / $numberOfClasses);
	for ($ii = 0; $ii < $numberOfClasses; $ii++) {
		$classes[] = $classSize;
	}
	$classes[$ii - 1] = $numberOfValues - ($numberOfClasses - 1) * $classSize;

	/**
	  * Now that we have our simple quantile split, we'll do our first round of adjustments. It's very likely the quantile split
	  * caused equal values to be split into two different classes. This will not work for our classes. We will go through each
	  * class and determine if any of the values in the classes exist in another class. If they do, we will see which class
	  * would be best for that set of values by creating feaux classes as if all of the values have been moved and determine which 
	  * move would provide the lowest sum of squared differences for that value. We will then move those values into that class.
	  */
	$valueCounts = array_count_values($values);
	$changeOccurred = true;
	$firstIterationCounter = 0;
	do {
		$changeOccurred = false;
		if ($numberOfClasses == 6) {
			$numsixcounter++;
			if ($numsixcounter == 20) {
				exit;
			}
		}
		$startingValuesKey = 0;
		$currentClassesArray = array();
		foreach ($classes as $numberValuesInClass) {
			$currentClassesArray[] = array_slice($values, $startingValuesKey, $numberValuesInClass);
			$startingValuesKey += $numberValuesInClass;
		}
		foreach ($currentClassesArray as $key => $class) {
			if ($key == $numberOfClasses - 1) {
				break;
			}
			/**
			  * Go through each class. If the class only has one number, we are good. Let's move the rest of the numbers 
			  * into this class if they exist elsewhere
			  */
			if (count(array_unique($class)) == 1) {
				$onlyValueInClass = $class[0];
				if ($classes[$key] != $valueCounts[$onlyValueInClass]) {
					// Then there are other classes with this value. We've got some moving to do.
					$numberOfValuesToMove = $valueCounts[$onlyValueInClass] - $classes[$key];
					$classKeyToTry = $key + 1;
					while ($numberOfValuesToMove > 0) {
						// We have to start subtracting from classes that are suitable
						if ($classes[$classKeyToTry] <= 1) {
							do {
								$classKeyToTry++;
								if ($classKeyToTry > $numberOfClasses - 1) {
									$classKeyToTry = 0;
								}
							} while ($classKeyToTry == $key);
						}
						$classes[$classKeyToTry]--;
						$classes[$key]++;
						$numberOfValuesToMove--;					
					}
					$changeOccurred = true;
					break;
				}
			} else {
				// There are more than one value in this class
				$valuesInThisClass = array_count_values($class);
				$value = max($class);
				$numberTimesValueInClass = $valuesInThisClass[$value];
				if ($numberTimesValueInClass != $valueCounts[$value]) {
					/**
					  * Then there are more of these in a different class. If the next class is nothing but this value, we 
					  * know we will just move the values to that class.
					  */
					if (count(array_unique($currentClassesArray[$key + 1])) == 1) {
						// The next class up is made up entirely of this class. We will move the numbers to it.
						$numberValuesToMove = $numberTimesValueInClass;
						for ($ii = 0; $ii < $numberValuesToMove; $ii++) {
							$classes[$key]--;
							$classes[$key + 1]++;
						}
						if ($classes[$key + 1] != $valueCounts[$value]) {
							// Then we may have moved all the values out of this class into the next, but there are still more
							$numberLeftToMove = $valueCounts[$value] - $classes[$key + 1];
							$classKeyToTry = $key + 2;
							while ($numberLeftToMove > 0) {
								// We have to start subtracting from classes that are suitable
								if ($classes[$classKeyToTry] <= 1) {
									$classKeyToTry++;
								}
								$classes[$classKeyToTry]--;
								$classes[$key + 1]++;
								$numberLeftToMove--;					
							}
						}	
					} else {
						/**
						  * There are other numbers in the next class besides the one we are working with. Let's create
						  * the two classes as if we had put all of the values in the class. Then, we'll find out which 
						  * provides the best SSD for our current $value. 
						  */
						$firstComparisonClass = $currentClassesArray[$key];
						$secondComparisonClass = $currentClassesArray[$key + 1];
						$numberValuesForClass = array_count_values($firstComparisonClass);
						$numberValuesToAddFirstClass = $valueCounts[$value] - $numberValuesForClass[$value];
						for ($ii = 0; $ii < $numberValuesToAddFirstClass; $ii++) {
							$firstComparisonClass[] = $value;
						}
						$firstClassAverage = calculateAverage($firstComparisonClass);
						$numberValuesForClass = array_count_values($secondComparisonClass);
						$numberValuesToAddSecondClass = $valueCounts[$value] - $numberValuesForClass[$value];
						for ($ii = 0; $ii < $numberValuesToAddSecondClass; $ii++) {
							$secondComparisonClass[] = $value;
						}
						$secondClassAverage = calculateAverage($secondComparisonClass);

						// Now that we have built our two feaux classes, let's see which provides us with the best SSD for the value
						$firstSSD = pow($value - $firstClassAverage, 2);
						$secondSSD = pow($value - $secondClassAverage, 2);
						if ($firstSSD < $secondSSD) {
							$classKeyToAddTo = $key;
							$classKeyToSubtractFrom = $key + 1;
							$numberValuesToMove = $numberValuesToAddFirstClass;
						} else {
							$classKeyToAddTo = $key + 1;
							$classKeyToSubtractFrom = $key;
							$numberValuesToMove = $numberValuesToAddSecondClass;
						}
						for ($ii = 0; $ii < $numberValuesToMove; $ii++) {
							$classes[$classKeyToAddTo]++;
							$classes[$classKeyToSubtractFrom]--;
						}
					}
					$changeOccurred = true;
					break;
				}
			}
		}
	} while ($changeOccurred == true);

	/**
	  * Now that we are sure our classes have been split in a way that values are not spread amongst different classes, 
	  * we can do work optimizing our classes further. We will look at the highest and lowest values for each class and 
	  * determine if those sets of values would be better suited in the class above, below, or if they are good where
	  * they are at. We do not need to look at values in the middle of each class because moving a value in the middle
	  * to a class above or below it would put our classes out of numeric order and does not make sense. We also do not
	  * look at the largest or smallest values because those should stay in their lowest and highest class respsectively.
	  */
	$changeOccurred = 1;
	$iterationCounter = 0;
	$distinctValues = array_keys($valueCounts);
	$numberDistinctValues = count($distinctValues);
	$currentClassesArray = array();
	$startingValuesKey = 0;
	foreach ($classes as $numberValuesInClass) {
		$currentClassesArray[] = array_slice($values, $startingValuesKey, $numberValuesInClass);
		$startingValuesKey += $numberValuesInClass;
	}
	
	do {
		$changeOccurred = 0;

		// We only want to work on the minimums and maximums of the classes
		$minimumValue = min($values);
		$maximumValue = max($values);
		$valuesToWorkWith = array();
		foreach ($currentClassesArray as $class) {
			// We don't want to check values that are in classes by themselves because we cannot improve them
			if (count(array_unique($class)) != 1) {
				$minValueForArray = min($class);
				if ($minValueForArray != $minimumValue && $minValueForArray != $maximumValue) {
					$valuesToWorkWith[] = $minValueForArray;
				}
				$maxValueForArray = max($class);
				if ($maxValueForArray != $minimumValue && $maxValueForArray != $maximumValue) {
					$valuesToWorkWith[] = $maxValueForArray;
				}
			}
		}

		$numberOfValuesToWorkWith = count($valuesToWorkWith);
		if ($numberOfValuesToWorkWith > 0) {
			for ($ii = 0; $ii < $numberOfValuesToWorkWith; $ii++) {
				$iterationCounter++;
				$thisValue = $valuesToWorkWith[$ii];
				
				/**
				  * We will need to create feaux classes above and below the current class to see if the squared deviation decreases.
				  * If it does, we'll move the values into that class.
				  */
				$currentClassKeyForValue = determineClass(array_search($thisValue, $values), $numberOfClasses, $classes);
				
				$firstComparisonClassKey = $currentClassKeyForValue - 1;
				$secondComparisonClassKey = $currentClassKeyForValue + 1;
				$squaredDeviationsArray = array();
				if ($firstComparisonClassKey > 0) {
					$firstComparisonClass = $currentClassesArray[$firstComparisonClassKey];
					$numberValuesForClass = array_count_values($firstComparisonClass);
					$numberValuesToAddFirstClass = $valueCounts[$thisValue] - $numberValuesForClass[$thisValue];
					for ($jj = 0; $jj < $numberValuesToAddFirstClass; $jj++) {
						$firstComparisonClass[] = $thisValue;
					}
					$firstClassAverage = calculateAverage($firstComparisonClass);
					$squaredDeviationsArray[$firstComparisonClassKey] = pow($thisValue - $firstClassAverage, 2);
				}
				if ($secondComparisonClassKey < $numberOfClasses) {
					$secondComparisonClass = $currentClassesArray[$secondComparisonClassKey];
					$numberValuesForClass = array_count_values($secondComparisonClass);
					$numberValuesToAddSecondClass = $valueCounts[$thisValue] - $numberValuesForClass[$thisValue];
					for ($jj = 0; $jj < $numberValuesToAddSecondClass; $jj++) {
						$secondComparisonClass[] = $thisValue;
					}
					$secondClassAverage = calculateAverage($secondComparisonClass);
					$squaredDeviationsArray[$secondComparisonClassKey] = pow($thisValue - $secondClassAverage, 2);
				}

				$currentClassAverage = calculateAverage($currentClassesArray[$currentClassKeyForValue]);
				$currentSquaredDeviation = $squaredDeviationsArray[$currentClassKeyForValue] = pow($thisValue - $currentClassAverage, 2);

				$minSquaredDeviation = min($squaredDeviationsArray);
				if ($minSquaredDeviation != $currentSquaredDeviation) {
					$minSquaredDeviationKey = array_search($minSquaredDeviation, $squaredDeviationsArray);

					// Then we need to move these values from the class they are in to the class they should be in
					$numberOfThisValue = $valueCounts[$thisValue];
					$classes[$minSquaredDeviationKey] += $numberOfThisValue;
					$classes[$currentClassKeyForValue] -= $numberOfThisValue;
					$changeOccurred = 1;

					// Regenerate our classes as they currently are
					$startingValuesKey = 0;
					$currentClassesArray = array();
					foreach ($classes as $numberValuesInClass) {
						$currentClassesArray[] = array_slice($values, $startingValuesKey, $numberValuesInClass);
						$startingValuesKey += $numberValuesInClass;
					}
				}
			}
		}
	} while ($changeOccurred == 1);

	return getClassMaximums($values, $classes);
}

/**
  * This function determines the optimum number of classes for a given set of values by calculating the goodness of variance fit (GVF)
  * for class sizes 4 - 7. It will return the maximum values for each class and the number of values for each class in an array for the
  * number of classes that best fits the data.
  *
  * @param array $values - the values you want to determine the optimum deviation for
  * @param int $minimumNumberOfClasses - the minimum number of classes you want to try
  * @param int $maximumNumberOfClasses - the maximum number of classes you want to try
  * @return array - the maximum values for each array and the number of values for each class
  */
function getOptimalClassInformation ($values, $minimumNumberOfClasses = 4, $maximumNumberOfClasses = 7) {
	// Make sure our values are sorted
	array_multisort($values);

	$numberOfUniqueValues = count(array_unique($values));
	if ($numberOfUniqueValues <= $maximumNumberOfClasses) {
		$maximumValues = getJenksClasses ($numberOfUniqueValues, $values);
		$numberOfValuesPerClass = getNumberOfValuesPerClass ($values, $maximumValues);
		return array ($maximumValues, $numberOfValuesPerClass);
	} else {
		$valuesAverage = calculateAverage($values);
		$SDAM = 0;
		foreach ($values as $value) {
			$SDAM += pow ($value - $valuesAverage, 2);
		}

		for ($classNumber = $minimumNumberOfClasses; $classNumber <= $maximumNumberOfClasses; $classNumber++) {
			$maximumValues = getJenksClasses ($classNumber, $values);
			$numberOfValuesPerClass = getNumberOfValuesPerClass ($values, $maximumValues);
			$arraySliceIndex = 0;
			$SDCM = 0;
			foreach ($numberOfValuesPerClass as $numberOfValues) {
				$thisClass = array_slice($values, $arraySliceIndex, $numberOfValues);
				$thisClassAverage = calculateAverage($thisClass);
				$deviationsSumForClass = 0;
				foreach ($thisClass as $thisValue) {
					$deviationsSumForClass += pow ($thisValue - $thisClassAverage, 2);
				}
				$SDCM += $deviationsSumForClass;
				$arraySliceIndex += $numberOfValues;
			}
			$gvfsArray[$classNumber] = 1 - ($SDCM / $SDAM);
			$returnArraysToClassNumbers[$classNumber] = array ($maximumValues, $numberOfValuesPerClass);
		}
	}

	return $returnArraysToClassNumbers[array_search(max($gvfsArray), $gvfsArray)];
}

/**
  * Takes an array of values and an array of numbers per class from Jenks to provide us with a nice list of what the ranges are
  *
  * @param array $values - the original array of values
  * @param array $jenksArray - the array of how many values should go in each class from Jenks
  */
function getMapKeys ($values, $jenksArray) {
	// Make sure our values are sorted
	array_multisort($values);

	if (count($jenksArray) == 2) {
		// If the Jenks array just contains a single value and the max, then we can just return that value
		return array (0 => $jenksArray[1]);
	}
	$returnArray = array();
	$startingValue = $jenksArray[0];
	$arrayCount = count($jenksArray);
	$rangeString = 1;
	$stoppingValue = $jenksArray[$arrayCount - 1];
	for ($ii = 1; $ii < $arrayCount; $ii++) {
		$maxValue = $jenksArray[$ii];
		if ($maxValue == $stoppingValue) {
			if ($rangeString == $maxValue) {
				$rangeString = $maxValue;
		 	} else {
				foreach ($values as $value) {
					if ($value < $maxValue) {
						$max = $value; 
					} else if ($rangeString == $max) {
						break;
					} else {
						$rangeString .= ' - ' . $max;
						break;
					}
				}
			}
		} else {
			foreach ($values as $value) {
				if ($value < $maxValue) {
					$max = $value; 
				} else if ($max == $rangeString) {
					break;
				} else {
					$rangeString .= ' - ' . $max;
					break;
				}
			}
		}

		$returnArray[] = $rangeString;
		$rangeString = $jenksArray[$ii];
	}

	return $returnArray;
}

/** 
  * This function will display a map using the Google Charts API. Information about the API can be found
  * here: http://code.google.com/apis/chart/types.html#maps
  *
  * We are using Jenks Natural Breaks Classification Scheme to create our breaks in our data and our keys
  * for our maps.
  *
  * The output for this will be a URI that looks like this: http://chart.apis.google.com/chart?cht=t
  *	&chs=440x220&chco=DCDCDC,FDFAD1,FFE9B0,FFBB7D,E5280C,A61900&chtm=usa&chd=t:20,20,20,20,20,20,20,20,
  * 20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,40,40,40,40,40,40,40,40,40,40,40,40,60,60,60,60,60,60,
  * 60,60,60,80,80,80,80,100,100&chld=VTHIDESDWVDCMERIWYARNENHAKNMMSLAOKIDIANVALUTSCCTKYTNINMDWIMNMOOR
  * MANCAZVAGAMIOHCOPANJILWAFLTXNYKSCAMT&chf=bg,s,EAF7FE
  *
  * Due to the limits of the numbers and formats of numbers that can be sent to the charting API, we break 
  * our classes up into even numbers that have the most distance between them as possible but still remain 
  * within 100. The rest of the arguments are fully explained in the API documentaiton.
  *
  * @param array $values - the values of the map you are trying to create
  * @param array $locations - either an array of 2-digit state codes or an array of ISO 3166-1-alpha-2 country 
  *						      codes. This array should correspond to the $values in the way it is sorted.
  * @param string $map_type - the type of map you would like. Should be from this list:
  *							  'africa', 'asia', 'europe', 'middle_east', 'south_america', 'usa', 'world'
  * @param boolean $return_data - if return data is set to true, this function will return the URI and the
  *								  colors and data needed to display the map key
  * @return mixed - either nothing or an array containing the return data
  */
function displayGoogleMap($values, $locations, $map_type, $return_data = false) {
	// Color of locations with no values
	$empty_color = 'DCDCDC';

	// Color of the water behind the maps
	$water_color = 'FAFAFA';

	// Make sure our values are sorted
	array_multisort($values);

	// We will grab the maximum values from each class as determined by the Jenks algorithm
	$class_information = getOptimalClassInformation($values);
	$jenks_max_values_per_class = $class_information[0];
	$number_values_per_class = $class_information[1];
	$number_of_classes = count($number_values_per_class);
  	$valid_map_types = array('africa', 'asia', 'europe', 'middle_east', 'south_america', 'usa', 'world');
	$display_map_types = array ('Africa', 'Asia', 'Europe', 'Middle East', 'South America', 'USA', 'World');

	// With this information, we will get our map keys
	$breaks_array = getMapKeys($values, $jenks_max_values_per_class);

	if ($number_of_classes <= 5) {
		$map_colors = array ($empty_color, 'FDFAD1', 'FFE9B0', 'FFBB7D', 'E5280C', 'A61900');
		$google_colors = array ($empty_color, 'FEECB6', 'FECC91', 'F4804F', 'D82509', 'A51900');

		// Google renders the colors for 2 classes in a particular way
		if ($number_of_classes == 2) {
			$google_colors = array ($empty_color, 'FEECB6', 'FECD91');
		}

		$class_multiplier = 20;
	} else if ($number_of_classes > 5) {
		$map_colors = array ($empty_color, 'FFFFFF', 'FDFAD1', 'FFE9B0', 'FFBB7D', 'FF7A3D', 'E5280C', 'A61900');
		$google_colors = array ($empty_color, 'FDFAD1', 'FDEDB9', 'FED095', 'FEA265', 'F96933', 'E2270B', 'AD1A01');

		// Google renders the colors for 6 classes in a particular way
		if ($number_of_classes == 6) {
			$google_colors = array ($empty_color, 'FDECB8', 'FCD095', 'FDA165', 'F86732', 'E2280B', 'AD1A01');
		}
		$map_colors = $google_colors;
		$class_multiplier = round(100 / $number_of_classes, 2);
	}

	// Let's build our URI
	$uri = 'http://chart.apis.google.com/chart?cht=t&chs=440x220&chco=';
	foreach ($map_colors as $color) {
		$uri .= $color . ',';
	}
	$uri = substr($uri, 0, -1);
	$uri .= '&chtm=' . $map_type;

	// Here we will build the location abbreviations and location values to go in the URI
	$max_value = $values[0];
	$key = 0;
	foreach ($locations as $location_abbrev => $number_from_location) {
		$location_codes .= $location_abbrev;
		$class_number = round((determineClass($key, $number_of_classes, $number_values_per_class) + 1) * $class_multiplier);
		$location_values .= $class_number . ',';
		$key++;
	}
	$location_values = substr($location_values, 0, -1);

	// Finish off our URI by tacking on the values, codes, and color for the water
	$uri .= '&chd=t:' . $location_values .
			'&chld=' . $location_codes .
			'&chf=bg,s,' . $water_color;

	// We need to check and see if they just wanted data returned or if they wanted the map displayed
	if ($return_data) {
		// Let's build our array for the map colors and data and return our data
		$map_key_array[$empty_color] = 'No Data';
		for ($ii = 1; $ii <= $number_of_classes; $ii++) {
			$color = $google_colors[$ii];
			$text = $breaks_array[$ii - 1];
			$map_key_array[$color] = $text;
		}			
		return array ($uri, $map_key_array);
	} else {
		// Let's display it
		$empty_color = $google_colors[0];
        echo <<<HTML
<div class="map_legend">
    <table>
        <tr>
            <td class="mapcolor" bgcolor="#<?php echo $map_colors[0]; ?>">
                &nbsp;&nbsp;&nbsp;
            </td>
            <td>
                No Data
            </td>
        </tr>
HTML;
		for ($ii = 1; $ii <= $number_of_classes; $ii++) {
			$color = $google_colors[$ii];
			$text = $breaks_array[$ii - 1];
			echo <<<HTML
        <tr>
            <td class="mapcolor" bgcolor="#{$color}" border="1">&nbsp;&nbsp;&nbsp;</td>
            <td>{$text}</td>
        </tr>
HTML;

		}
        echo <<<HTML
    </table>
</div>
<img {$margin}src="{$uri}">
HTML;
	} 
} 
?>