QCPAxis *yAxis = ui->customPlot->yAxis; double minY = std::numeric_limits<double>::max(); double maxY = std::numeric_limits<double>::min(); for (int i = 0; i < ui->customPlot->graphCount(); i++) { QCPGraph *graph = ui->customPlot->graph(i); if (graph->dataCount() == 0) { continue; } QCPGraphDataContainer::const_iterator it = graph->data().constBegin(); for (; it != graph->data().constEnd(); ++it) { double value = it->value; if (value < minY) { minY = value; } if (value > maxY) { maxY = value; } } } double range = qMax(qAbs(minY), qAbs(maxY)) * 2; double center = (minY + maxY) / 2; yAxis->setRange(center - range, center + range); 多条y轴，不是所有曲线共用y轴

如果多条曲线不是共用一个y轴，那么你需要对每个y轴分别进行自适应范围的计算和设置。

具体步骤如下：

1. 获取所有y轴的指针，可以通过QCustomPlot::axisRect()的成员函数axis()来获取。

QList<QCPAxis*> yAxisList;
for (int i = 0; i < ui->customPlot->axisRectCount(); i++) {
    QCPAxisRect *axisRect = ui->customPlot->axisRect(i);
    QCPAxis *yAxis = axisRect->axis(QCPAxis::atLeft);
    if (yAxis != nullptr) {
        yAxisList.append(yAxis);
    }
}

2. 遍历每个y轴对应的曲线，获取最小值和最大值。

double minY = std::numeric_limits<double>::max();
double maxY = std::numeric_limits<double>::min();
for (int i = 0; i < yAxisList.length(); i++) {
    QCPAxis *yAxis = yAxisList[i];
    minY = std::numeric_limits<double>::max();
    maxY = std::numeric_limits<double>::min();
    for (int j = 0; j < ui->customPlot->graphCount(); j++) {
        QCPGraph *graph = ui->customPlot->graph(j);
        if (graph->dataCount() == 0) {
            continue;
        }
        if (graph->valueAxis() != yAxis) {
            continue;
        }
        QCPGraphDataContainer::const_iterator it = graph->data().constBegin();
        for (; it != graph->data().constEnd(); ++it) {
            double value = it->value;
            if (value < minY) {
                minY = value;
            }
            if (value > maxY) {
                maxY = value;
            }
        }
    }
}

3. 计算自适应的范围，并设置每个y轴的范围。

double range = qMax(qAbs(minY), qAbs(maxY)) * 2;
double center = (minY + maxY) / 2;
for (int i = 0; i < yAxisList.length(); i++) {
    QCPAxis *yAxis = yAxisList[i];
    yAxis->setRange(center - range, center + range);
}

完整代码示例：

QList<QCPAxis*> yAxisList;
for (int i = 0; i < ui->customPlot->axisRectCount(); i++) {
    QCPAxisRect *axisRect = ui->customPlot->axisRect(i);
    QCPAxis *yAxis = axisRect->axis(QCPAxis::atLeft);
    if (yAxis != nullptr) {
        yAxisList.append(yAxis);
    }
}
for (int i = 0; i < yAxisList.length(); i++) {
    QCPAxis *yAxis = yAxisList[i];
    double minY = std::numeric_limits<double>::max();
    double maxY = std::numeric_limits<double>::min();
    for (int j = 0; j < ui->customPlot->graphCount(); j++) {
        QCPGraph *graph = ui->customPlot->graph(j);
        if (graph->dataCount() == 0) {
            continue;
        }
        if (graph->valueAxis() != yAxis) {
            continue;
        }
        QCPGraphDataContainer::const_iterator it = graph->data().constBegin();
        for (; it != graph->data().constEnd(); ++it) {
            double value = it->value;
            if (value < minY) {
                minY = value;
            }
            if (value > maxY) {
                maxY = value;
            }
        }
    }
    double range = qMax(qAbs(minY), qAbs(maxY)) * 2;
    double center = (minY + maxY) / 2;
    yAxis->setRange(center - range, center + range);
}