GET_Y_FX

About the function

The function looks up in an xy-relation, defined as argument to the function, with values from a time series that also is an argument to the function. The result is the y-value from the xy-relation, possibly interpolated. See also information about how to handle input values outside the provided range.

Syntax

• GET_Y_FX (t,D,D[,s])

Description

#	Type	## Description
1	t	Series containing x-values used to lookup in the xy-relation to find the result value for current point of time.
2	D	X-values, sorted increasingly.
3	D	Y-values corresponding to the X-values given in the last argument.
4	s	Can have the following values: INTERPOL - means that the y-value is interpolated, default is no interpolation NOHOLD - means that if you have a NaN on the X-series, the last calculated Y-value is not used. In default mode last calculated value is used. You may combine these two methods and separate them by using a comma.

GET_Y_FX (t,D,D,[s]) corresponds to y=f(x)

Example 1

R1 = @GET_Y_FX(%'/X series',{-1,20,40}, {1,2,3} )
R2 = @GET_Y_FX(%'/X series',{-1,20,40}, {1,2,3}, 'INTERPOL')
R3 = @GET_Y_FX(%'/X series',{-1,20,40}, {1,2,3}, 'INTERPOL,NOHOLD' )

This gives the following values for an X-series presented in the first column.

The function is best explained by an illustration:

You state a curve band, iso curves in the form of an array of time series. These are associated with an array of y-values. In the above illustration the y-values are -1, 20 and 40, and time series 1 is associated with value -1, time series 2 with 20 and time series 3 with 40. The thickest black curve represents values on the input data series. In the points where this crosses the iso curves, a new result value is generated, as the blue curve shows.

Handle input values outside the provided range

When an input is lower than the first value from the x range provided in the function call (-1 in the example below) the first value from the y range will be returned (1 in the example below).

When an input is higher than the last value from the x range provided in the function call (40 in the example below) the last value from the y range will be returned (3 in the example below).

Example 2

##=@GET_Y_FX(@t('t'), {-1,20,40}, {1,2,3}, 'INTERPOL,NOHOLD')

input	output
-10	1
2	1.142
10	1.523
NaN	NaN
30	2.5
NaN	NaN
50	3

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