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Last Modified: January 12, 2018

Interpolates or extrapolates a function *f* by using a polynomial function. The polynomial function passes through all the points formed by arrays of dependent and independent values.

The polynomial method is not suitable for exploratory calculation. Compared with the spline method, the polynomial method yields the interpolation result with extreme derivatives.

A Boolean that specifies whether the values of the independent variable increase monotonically with the index.

True | The values of the independent variable increase monotonically with the index. This node does not sort x or reorder y. |

False | The values of the independent variable does not increase monotonically with the index. This node sorts x to be in ascending order and reorders y accordingly. |

This input is available only if you wire an array of double-precision, floating-point numbers to **x** or **y**.

**Default: **False

Tabulated values of the dependent variable.

This input accepts a double-precision, floating-point number or a 1D array of double-precision, floating-point numbers.

When **x** and **y** are 1D arrays of double-precision, floating-point numbers, the length of **x** must equal the length of **y**.

Tabulated values of the independent variable.

This input accepts a double-precision, floating-point number or a 1D array of double-precision, floating-point numbers.

When **x** and **y** are 1D arrays of double-precision, floating-point numbers, the length of **x** must equal the length of **y**.

Points at which the interpolation or extrapolation is performed.

This input accepts a double-precision, floating-point number or a 1D array of double-precision, floating-point numbers.

If the value of **xi** is in the range of **x**, the node performs interpolation. Otherwise, the node performs extrapolation. If **xi** is too far from the range of **x**, the extrapolation error may be large. It is not a satisfactory extrapolation.

Number of times that this node interpolates values repeatedly and evenly between each **x** element to generate **xi used**. **ntimes** determines the locations of the interpolation values.

This input yields interpolated values between every **y** element when **xi** is empty. The node ignores **ntimes** if you wire the **xi** input.

This input is available only if you wire an array of double-precision, floating-point numbers to **xi**.

**Default: **1

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an **error in** input and an **error out** output so that the node can respond to and communicate errors that occur while code is running. The value of **error in** specifies whether an error occurred before the node runs. Most nodes respond to values of **error in** in a standard, predictable way.

**Default: **No error

Interpolation of the function *f* at the points you specified.

This output can return a double-precision, floating-point number or a 1D array of double-precision, floating-point numbers.

Values of the independent variable at which this node computes interpolated values of the dependent variable.

This output is available only if you wire an array of double-precision, floating-point numbers to **xi**.

If **xi** is empty, **xi used** returns 2^{ntimes} *(*N* - 1) + 1 points with (2^{ntimes} - 1) points located evenly between each two adjacent elements in **x**, where *N* is the length of **x**. If you wire the **xi** input, **xi used** equals **xi**.

An estimate of the errors for each interpolated values.

This output can return a double-precision, floating-point number or a 1D array of double-precision, floating-point numbers.

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

**error in** input and an **error out** output so that the node can respond to and communicate errors that occur while code is running. The value of **error in** specifies whether an error occurred before the node runs. Most nodes respond to values of **error in** in a standard, predictable way.

This node calculates the interpolation value using the following equation: **yi** = *P*(*x*), where *P* is the unique polynomial of degree *n* - 1 that passes through the *n* points (*x*_{i}, *y*_{i}).

**Where This Node Can Run: **

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application