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interpolateLinear.js
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interpolateLinear.js
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/*
* Copyright (C) 2015 Stefano D'Angelo <zanga.mail@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* Does simple linear interpolation.
* Writes countOut samples in yi starting from index firstOut, reading countIn
* samples from y starting from index firstIn. x represents input x coordinates,
* xi represents output x coordinates. Both x and xi are expected to be ordered
* and non-decreasing. It produces NaNs for xi coordinates outside of x ranges
* (i.e., no extrapolation is performed). */
canvasPlot.interpolateLinear = function (x, y, xi, yi, firstIn, firstOut,
countIn, countOut) {
var i = firstOut;
var nextOut = firstOut + countOut;
for (; i < nextOut && xi[i] < x[firstIn]; i++)
yi[i] = NaN;
var j = firstIn + 1;
var lastIn = firstIn + countIn - 1;
outer:
for (; i < nextOut; i++) {
while (xi[i] >= x[j]) {
j++;
if (j == lastIn) {
yi[i] = xi[i] == x[j] ? y[j] : NaN;
i++;
break outer;
}
}
var jl = j - 1;
yi[i] = y[jl] + (y[j] - y[jl]) * (xi[i] - x[jl])
/ (x[j] - x[jl]);
}
for (; i < nextOut; i++)
yi[i] = NaN;
};