* result is {@link Double#NaN}. If it contains {@link Double#POSITIVE_INFINITY} and finite values
   * only or {@link Double#POSITIVE_INFINITY} only, the result is {@link Double#POSITIVE_INFINITY}.
   * If it contains {@link Double#NEGATIVE_INFINITY} and finite values only or {@link
   * Double#NEGATIVE_INFINITY} only, the result is {@link Double#NEGATIVE_INFINITY}.
   *

   * result is {@link Double#NaN}. If it contains {@link Double#POSITIVE_INFINITY} and finite values
   * only or {@link Double#POSITIVE_INFINITY} only, the result is {@link Double#POSITIVE_INFINITY}.
   * If it contains {@link Double#NEGATIVE_INFINITY} and finite values only or {@link
   * Double#NEGATIVE_INFINITY} only, the result is {@link Double#NEGATIVE_INFINITY}.
   *

    if (lower == NEGATIVE_INFINITY) {
      if (upper == POSITIVE_INFINITY) {
        // Return NaN when lower == NEGATIVE_INFINITY and upper == POSITIVE_INFINITY:
        return NaN;
      }
      // Return NEGATIVE_INFINITY when NEGATIVE_INFINITY == lower <= upper < POSITIVE_INFINITY:
      return NEGATIVE_INFINITY;
    }
    if (upper == POSITIVE_INFINITY) {

        .containsExactly(
            0, NEGATIVE_INFINITY,
            1, NEGATIVE_INFINITY, // interpolating between NEGATIVE_INFINITY and 1.0
            2, 1.0,
            8, 4.0,
            9, 4.5,
            10, 5.0);
  }

  public void testScale_index_compute_doubleCollection_negativeInfinity() {
    // interpolating between NEGATIVE_INFINITY and 1.0

        .containsExactly(
            0, NEGATIVE_INFINITY,
            1, NEGATIVE_INFINITY, // interpolating between NEGATIVE_INFINITY and 1.0
            2, 1.0,
            8, 4.0,
            9, 4.5,
            10, 5.0);
  }

  public void testScale_index_compute_doubleCollection_negativeInfinity() {
    // interpolating between NEGATIVE_INFINITY and 1.0

import static com.google.common.math.StatsTesting.megaPrimitiveDoubleStream;
import static com.google.common.truth.Truth.assertThat;
import static com.google.common.truth.Truth.assertWithMessage;
import static java.lang.Double.NEGATIVE_INFINITY;
import static java.lang.Double.NaN;
import static java.lang.Double.POSITIVE_INFINITY;
import static java.lang.Math.sqrt;
import static java.util.Arrays.stream;
import static org.junit.Assert.assertThrows;

   * times, due to numerical errors.
   *
   * <h3>Non-finite values</h3>
   *
   * <p>If the dataset contains any non-finite values ({@link Double#POSITIVE_INFINITY}, {@link
   * Double#NEGATIVE_INFINITY}, or {@link Double#NaN}) then the result is {@link Double#NaN}.
   *
   * @throws IllegalStateException if the dataset is empty
   */
  public double populationCovariance() {
    checkState(count() != 0);

   * times, due to numerical errors.
   *
   * <h3>Non-finite values</h3>
   *
   * <p>If the dataset contains any non-finite values ({@link Double#POSITIVE_INFINITY}, {@link
   * Double#NEGATIVE_INFINITY}, or {@link Double#NaN}) then the result is {@link Double#NaN}.
   *
   * @throws IllegalStateException if the dataset is empty
   */
  public double populationCovariance() {
    checkState(count() != 0);

      for (double first : ImmutableList.of(1.1, POSITIVE_INFINITY, NEGATIVE_INFINITY, NaN)) {
        values[0] = first;
        values[1] = -44.44;
        for (double third : ImmutableList.of(33.33, POSITIVE_INFINITY, NEGATIVE_INFINITY, NaN)) {
          values[2] = third;
          values[3] = 555.555;
          for (double fifth : ImmutableList.of(-2.2, POSITIVE_INFINITY, NEGATIVE_INFINITY, NaN)) {
            values[4] = fifth;

      for (double first : ImmutableList.of(1.1, POSITIVE_INFINITY, NEGATIVE_INFINITY, NaN)) {
        values[0] = first;
        values[1] = -44.44;
        for (double third : ImmutableList.of(33.33, POSITIVE_INFINITY, NEGATIVE_INFINITY, NaN)) {
          values[2] = third;
          values[3] = 555.555;
          for (double fifth : ImmutableList.of(-2.2, POSITIVE_INFINITY, NEGATIVE_INFINITY, NaN)) {
            values[4] = fifth;