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(C++) Rescale

Math code snippet to rescale a double, 1D std::vector or 2D std::vector from a certain range to a new range.

Rescale on a double

#include <cassert>

#include <algorithm>

//From http://www.richelbilderbeek.nl/CppRescale.htm

const double Rescale(

const double value,

const double oldMin,

const double oldMax,

const double newMin,

const double newMax)

{

assert(value >= oldMin);

assert(value <= oldMax);

const double oldDistance = oldMax - oldMin;

//At which relative distance is value on oldMin to oldMax ?

const double distance = (value - oldMin) / oldDistance;

assert(distance >= 0.0);

assert(distance <= 1.0);

const double newDistance = newMax - newMin;

const double newValue = newMin + (distance * newDistance);

assert(newValue >= newMin);

assert(newValue <= newMax);

return newValue;

}

Rescale on a 1D std::vector

#include <cassert>

#include <algorithm>

#include <vector>

//From http://www.richelbilderbeek.nl/CppRescale.htm

const std::vector<double> Rescale(

std::vector<double> v,

const double newMin,

const double newMax)

{

const double oldMin = *std::min_element(v.begin(),v.end());

const double oldMax = *std::max_element(v.begin(),v.end());

typedef std::vector<double>::iterator Iter;

Iter i = v.begin();

const Iter j = v.end();

for ( ; i!=j; ++i)

{

*i = Rescale(*i,oldMin,oldMax,newMin,newMax);

}

return v;

}

Rescale on a 2D std::vector

#include <cassert>

#include <algorithm>

#include <vector>

//From http://www.richelbilderbeek.nl/CppRescale.htm

const std::vector<std::vector<double> > Rescale(

std::vector<std::vector<double> > v,

const double newMin,

const double newMax)

{

const double oldMin = MinElement(v);

const double oldMax = MaxElement(v);

typedef std::vector<std::vector<double> >::iterator RowIter;

RowIter y = v.begin();

const RowIter maxy = v.end();

for ( ; y!=maxy; ++y)

{

typedef std::vector<double>::iterator ColIter;

ColIter x = y->begin();

const ColIter maxx = y->end();

for ( ; x!=maxx; ++x)

{

*x = Rescale(*x,oldMin,oldMax,newMin,newMax);

}

}

return v;

}

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