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INTERPOLATE
Attachment | Size | |
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INTERPOLATE.xlsx |
computes new data points within the range of a set of known data points.
Syntax
INTERPOLATE(X, Y, target, Method, extrapolation in Excel)
X
is the x-component of the input data table (a one dimensional array of cells (e.g. rows or columns)).
Y
is the y-component (i.e. function) of the input data table (a one dimensional array of cells (e.g. rows or columns)).
target
is the desired x-value(s) to interpolate for (a single value or a one dimensional array of cells (e.g. rows or columns)).
Method
is the interpolation in Excel method (1=Forward Flat, 2=Backward Flat, 3=Linear, 4=Cubic Spline).
Value | Method |
---|---|
1 | Forward Flat |
2 | Backward Flat |
3 | Linear (default) |
4 | Cubic Spline |
extrapolation in Excel
sets whether or not to allow extrapolation (1=Yes, 0=No). If missing, the default is to not allow extrapolation.
Value | Extrapolation in Excel |
---|---|
0 | No (default) |
1 | Yes |
Remarks
- The X and Y array sizes must be identical.
- The X-array and Y-array both consist of numerical values. Dates in Excel are internally represented by numbers.
- The values in the X-array can be unsorted and may have duplicate values.
- In the case where X has duplicate values, INTERPOLATE will replace those duplicate values with a single entry, setting the corresponding y-value equal to the average.
- The X and/or Y arrays may have missing values (#N/A). In this case, INTERPOLATE will remove those entries.
- For cubic spline interpolation, we construct a set of natural cubic splines that are twice continuously differentiable functions to yield the least oscillation about the function f which is found by interpolation in Excel.
Examples
References
- Kincaid, David; Ward Cheney (2002). Numerical Analysis (3rd edition). Brooks/Cole. ISBN 0-534-38905-8. Chapter 6.
- Ahlberg, Nielson, and Walsh, The Theory of Splines and Their Applications, 1967.
Attachment | Size |
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INTERPOLATE.xlsx | 20.25 KB |