[Function]

(interpl x envelope {keyword value}*)

Returns the interpolated y value of x in envelope, a list of xy coordinate pairs. The return value can be optionally scaled and offset according to the keyword arguments.

interpl supports the following keyword arguments:

:base number

If number is 1 then linear interpolation is performed. If number is greater or less than one then the return value follows an exponential where values greater than 1 produce concave curves and values less than 1 but greater than 0 produce convex curves. The default value is 1.

:scale number

Multiplies the return value by number. The default value is 1.

:offset number

Adds number to the return value after scaling. The default value is 0.

:min number

An alternate name for specifying an offset.

:max number

Sets the multiplier to max-min and the offset to min.

Examples:

(interpl 50 '(0 0 100 1) :scale 2 :offset 3)
⇒ 4.0
(interpl 50 '(0 0 100 1) :min -5 :max 5)
⇒ 0.0

(interpl 50 '(0 0 100 1) :base 10)
⇒ 0.24025308
(interpl 50 '(0 0 100 1) :base .1 )
⇒ 0.7597469
(interpl 50 '(0 0 100 1) :base .1 :scale 1000)
⇒ 759.7469

See also:

• interp [Function]
• lookup [Function]
• Plotter [Topic]
• rescale-envelope [Function]
• tendency [Function]