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// Copyright 2019 Hans Dembinski
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt
// or copy at http://www.boost.org/LICENSE_1_0.txt)
//[ guide_axis_with_transform
#include <boost/histogram/axis/regular.hpp>
#include <limits>
int main() {
using namespace boost::histogram;
// make a regular axis with a log transform over [10, 100), [100, 1000), [1000, 10000)
axis::regular<double, axis::transform::log> r_log{3, 10., 10000.};
// log transform:
// - useful when values vary dramatically in magnitude, like brightness of stars
// - edges are not exactly at 10, 100, 1000, because of finite floating point precision
// - values >= 0 but smaller than the starting value of the axis are mapped to -1
// - values < 0 are mapped to `size()`, because the result of std::log(value) is NaN
assert(r_log.index(10.1) == 0);
assert(r_log.index(100.1) == 1);
assert(r_log.index(1000.1) == 2);
assert(r_log.index(1) == -1);
assert(r_log.index(0) == -1);
assert(r_log.index(-1) == 3);
// make a regular axis with a sqrt transform over [4, 9), [9, 16), [16, 25)
axis::regular<double, axis::transform::sqrt> r_sqrt{3, 4., 25.};
// sqrt transform:
// - bin widths are more mildly increasing compared to log transform
// - axis starting at value == 0 is ok, sqrt(0) == 0 unlike log transform
// - values < 0 are mapped to `size()`, because the result of std::sqrt(value) is NaN
assert(r_sqrt.index(0) == -1);
assert(r_sqrt.index(4.1) == 0);
assert(r_sqrt.index(9.1) == 1);
assert(r_sqrt.index(16.1) == 2);
assert(r_sqrt.index(25.1) == 3);
assert(r_sqrt.index(-1) == 3);
// make a regular axis with a power transform x^1/3 over [1, 8), [8, 27), [27, 64)
using pow_trans = axis::transform::pow;
axis::regular<double, pow_trans> r_pow(pow_trans{1. / 3.}, 3, 1., 64.);
// pow transform:
// - generalization of the sqrt transform
// - starting the axis at value == 0 is ok for power p > 0, 0^p == 0 for p > 0
// - values < 0 are mapped to `size()` if power p is not a positive integer
assert(r_pow.index(0) == -1);
assert(r_pow.index(1.1) == 0);
assert(r_pow.index(8.1) == 1);
assert(r_pow.index(27.1) == 2);
assert(r_pow.index(64.1) == 3);
assert(r_pow.index(-1) == 3);
}
//]
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