CODEWITHSUNDEEP
r
geotheory
geotheory

Reputation: 23660

Normalising data / mapping between data ranges

Does anyone know of a generic R function for mapping data between ranges? I can't find anything but this seems a pretty essential basic function. e.g.

map = function(x, xmin=NULL, xmax=NULL, tmin=0, tmax=1, na.rm=FALSE){
  if(is.null(xmin)) xmin = min(x)
  if(is.null(xmax)) xmax = max(x)
  x.range = xmax - xmin
  t.range = tmax - tmin
  ((x - xmin) / x.range * t.range + tmin)
}

.. would by default normalise from input data range to [0,1], but could also use a custom input range or map to specific outputs:

> v = -5:5
> map(v)
 [1] 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
> map(v, xmin=-10, xmax=10)
 [1] 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75
> map(v, tmax = 500)
 [1]   0  50 100 150 200 250 300 350 400 450 500

Am I reinventing the wheel?

Upvotes: 2

Views: 192

Answers (1)

baptiste
baptiste

Reputation: 77096

The scales package has one:

scales::rescale(v)
scales::rescale(v, from=c(-10, 10))

Upvotes: 3

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