android/guava/src/com/google/common/math/LinearTransformation.java
public static LinearTransformation horizontal(double y) {
    checkArgument(isFinite(y));
    double slope = 0.0;
    return new RegularLinearTransformation(slope, y);
  }
public static LinearTransformation horizontal(double y) {
    checkArgument(isFinite(y));
    double slope = 0.0;
    return new RegularLinearTransformation(slope, y);
  }
Builds an instance representing a horizontal transformation with a constant value of {@code y}.
(The inverse of this will be a vertical transformation.)