subsurface/stats/regressionitem.cpp
Dirk Hohndel 59fe2f3d7e cleanup: prevent distracing conversion warnings
We do want the -Wfloat-conversion warnings where they point out
potential bugs. But they are very distracting when they are triggered by
floating point literals (which the standard defines as double) passed to
a function expecting float arguments.

The fact that Qt6 changes the arguments to all these functions from
double to float is... hard to explain, but it is what it is. With these
changes, for the majority of cases we create inlined helpers that
conditionally compile to do the right thing. And in a handful of other
cases we simply cast to float (and accept that on Qt5 this then gets
cast back to double... for none of these cases the potential loss in
precision makes any difference, anyway - which likely is why the Qt
community made the decision to change the type of the arguments in the
first place).

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
2022-03-12 08:28:32 -08:00

102 lines
3.4 KiB
C++

// SPDX-License-Identifier: GPL-2.0
#include "regressionitem.h"
#include "statsaxis.h"
#include "statscolors.h"
#include "zvalues.h"
#include <cmath>
static const double regressionLineWidth = 2.0;
RegressionItem::RegressionItem(StatsView &view, regression_data reg,
StatsAxis *xAxis, StatsAxis *yAxis) :
ChartPixmapItem(view, ChartZValue::ChartFeatures),
xAxis(xAxis), yAxis(yAxis), reg(reg),
regression(true), confidence(true)
{
}
RegressionItem::~RegressionItem()
{
}
void RegressionItem::setFeatures(bool regressionIn, bool confidenceIn)
{
if (regressionIn == regression && confidenceIn == confidence)
return;
regression = regressionIn;
confidence = confidenceIn;
updatePosition();
}
// Note: this calculates the confidence area, even if it isn't shown. Might want to optimize this.
void RegressionItem::updatePosition()
{
if (!xAxis || !yAxis)
return;
auto [minX, maxX] = xAxis->minMax();
auto [minY, maxY] = yAxis->minMax();
auto [screenMinX, screenMaxX] = xAxis->minMaxScreen();
// Draw the confidence interval according to http://www2.stat.duke.edu/~tjl13/s101/slides/unit6lec3H.pdf p.5 with t*=2 for 95% confidence
QPolygonF poly;
const int num_samples = 101;
poly.reserve(num_samples * 2);
for (int i = 0; i < num_samples; ++i) {
double x = (maxX - minX) / (num_samples - 1) * static_cast<double>(i) + minX;
poly << QPointF(xAxis->toScreen(x),
yAxis->toScreen(reg.a * x + reg.b + 1.960 * sqrt(reg.res2 / (reg.n - 2) * (1.0 / reg.n + (x - reg.xavg) * (x - reg.xavg) / (reg.n - 1) * (reg.n -2) / reg.sx2))));
}
for (int i = num_samples - 1; i >= 0; --i) {
double x = (maxX - minX) / (num_samples - 1) * static_cast<double>(i) + minX;
poly << QPointF(xAxis->toScreen(x),
yAxis->toScreen(reg.a * x + reg.b - 1.960 * sqrt(reg.res2 / (reg.n - 2) * (1.0 / reg.n + (x - reg.xavg) * (x - reg.xavg) / (reg.n - 1) * (reg.n -2) / reg.sx2))));
}
QPolygonF linePolygon;
linePolygon.reserve(2);
linePolygon << QPointF(screenMinX, yAxis->toScreen(reg.a * minX + reg.b));
linePolygon << QPointF(screenMaxX, yAxis->toScreen(reg.a * maxX + reg.b));
QRectF box(QPointF(screenMinX, yAxis->toScreen(minY)), QPointF(screenMaxX, yAxis->toScreen(maxY)));
poly = poly.intersected(box);
linePolygon = linePolygon.intersected(box);
if (poly.size() < 2 || linePolygon.size() < 2)
return;
// Find lowest and highest point on screen. In principle, we need
// only check half of the polygon, but let's not optimize without reason.
double screenMinY = std::numeric_limits<double>::max();
double screenMaxY = std::numeric_limits<double>::lowest();
for (const QPointF &point: poly) {
double y = point.y();
if (y < screenMinY)
screenMinY = y;
if (y > screenMaxY)
screenMaxY = y;
}
screenMinY = floor(screenMinY - 1.0);
screenMaxY = ceil(screenMaxY + 1.0);
QPointF offset(screenMinX, screenMinY);
for (QPointF &point: poly)
point -= offset;
for (QPointF &point: linePolygon)
point -= offset;
ChartPixmapItem::resize(QSizeF(screenMaxX - screenMinX, screenMaxY - screenMinY));
img->fill(Qt::transparent);
if (confidence) {
QColor col(regressionItemColor);
col.setAlphaF((float)reg.r2);
painter->setPen(Qt::NoPen);
painter->setBrush(QBrush(col));
painter->drawPolygon(poly);
}
if (regression) {
painter->setPen(QPen(regressionItemColor, regressionLineWidth));
painter->drawLine(QPointF(linePolygon[0]), QPointF(linePolygon[1]));
}
ChartPixmapItem::setPos(offset);
}