**Restricted cubic spline** analysis of 30-day mortality with positive (a) and negative (b) fluctuations in Cl − within 72 h according to the cumulative fluid balance during 72 h after ICU admission. Cumulative fluid balance (%) was calculated as: (Total input fluid – total output fluid, L) × 100 x weight in admission (kg) − 1. 4. 15. · **Cubic** **splines** tend to be poorly behaved at the two tails (before the first **knot** and after the last **knot**). To avoid this, **restricted** **cubic** **splines** are used. A **r** **estricted** **cubic** **spline** is a **cubic** **spline** in which the **splines** are constrained to be linear in the two tails. Computes matrix that expands a single variable into the terms needed to fit a **restricted** **cubic** **spline** (natural **spline**) function using the truncated power basis. Two normalization options are given for somewhat reducing problems of ill-conditioning. The antiderivative function can be optionally created. If **knot** locations are not given, they will.

**restricted cubic spline**(b) used five user-specified

**knots**that were placed across the expected range of maximum change (50, 55, 60, 65, 70). This "fine tuning" provided a better fit and indicated that the lower maximum of the first

**restricted cubic spline**around the age of. Computes matrix that expands a single variable into the terms needed to fit a

**restricted cubic spline**(natural

**spline**) function using the truncated power basis. Two normalization options are given for somewhat reducing problems of ill-conditioning. The antiderivative function can be optionally created. If

**knot**locations are not given, they will be estimated from the marginal. mkspline— Linear and

**restricted cubic spline**construction 5

**Restricted cubic splines**A linear

**spline**can be used to ﬁt many functions well. However, a

**restricted cubic spline**may be a better choice than a linear

**spline**when working with a very curved function. When using a <b>

**restricted**</b> <b>

**cubic**</b> <b>

**spline**</b>, one obtains a continuous smooth function.