Fix a typo in cubic_interpolation.h
https://github.com/ceres-solver/ceres-solver/issues/439
Change-Id: Ib8c5b2511dd8b162784f387f1624d8568b3a57df
diff --git a/include/ceres/cubic_interpolation.h b/include/ceres/cubic_interpolation.h
index a26697b..4ff868a 100644
--- a/include/ceres/cubic_interpolation.h
+++ b/include/ceres/cubic_interpolation.h
@@ -116,7 +116,7 @@
// Example usage:
//
// const double data[] = {1.0, 2.0, 5.0, 6.0};
-// Grid1D<double, 1> grid(x, 0, 4);
+// Grid1D<double, 1> grid(data, 0, 4);
// CubicInterpolator<Grid1D<double, 1>> interpolator(grid);
// double f, dfdx;
// interpolator.Evaluator(1.5, &f, &dfdx);