15.5.617 table

table(x, y [, index], xnew [, /all, /middle])

table interpolates in table y vs. x at positions xnew. The first dimension of x and y specifies the entries in one interpolation table. Second and higher dimensions of x and y specify individual interpolation tables. x must be in ascending order in its first dimension. Dimensions shared between x and y must be equal. Variables are repeated to accomodate omitted dimensions. For example, if x has dimensions [2,3] and y dimensions [2,3,4,2] then x is repeated as needed to accomodate the third and fourth dimensions of y so that x effectively has the same dimensions as y.

If no index is specified, then keyword /all indicates that all values of xnew are to be used on each interpolation table. In that case, the result will have all expect the first of the (implied) dimensions of x and y, and all the dimensions of xnew, too.

If keyword /all is not specified, then each one-dimensional vector from xnew (e.g., xnew(*,2)) is applied to each next interpolation vector pair from x and y (e.g., x(*,2) and y(*,2)). In that case the second and higher dimensions of xnew must match the second and higher dimensions of x and y, and the result will have the same dimensions (real or implied) as xnew. For example, if x has dimensions [2,3], y dimensions [2,3,5], and xnew dimensions [4,3], then the result will have dimensions [4,3,5].

If index is specified, then it must be an array and each element of it determines which interpolation table (counting all dimensions of x, y except the first one) to use for the corresponding element of xnew. In that case, dimensions shared between index and xnew must be equal. Non-integer elements of index are treated with linear interpolation. The result gets all dimensions of the largest of xnew and index.

Keyword /middle (set by default) specifies that searching x for a value of xnew starts in the middle (and can then proceed either toward the beginning or the end of the interpolation table). If /nomiddle is specified, then searching starts at the beginning.

In earlier versions of LUX, a routine polate was available for linear interpolation. This older routine has now been superseded by table, and polate is now an alias of table.

Alias: polate

See also: tense