Php JPGraph错误，绘图的比例非法

我正试图用JPGragph制作一个图表，但我一直收到一个错误，上面说：

JpGraph Error A plot has an illegal scale. This could for example be that you are trying to use text auto scaling to draw a line plot with only one point or that the plot area is too small. It could also be that no input data value is numeric (perhaps only '-' or 'x')

$ydata = round($ydata[0]); // An attempt to convert float to int
$ydata = (int)$ydata; // That didn't bring any solution(thought it couldn't handle float)

$pt = new LinePlot($ydata); // Here is where the error is thrown
$bar2->Add($pt);
$pt->SetColor("blue");
$pt->SetWeight(10);

我尝试用整数替换$ydata，但这只会引发致命错误

如果没有圆形和类型转换，这是$ydata的var_转储：

array(1) { [0]=> float(8.1102970953135) }

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使用PHP7？我得到了相同的错误，并发现：

他们说你的PHP安装是“错误的”

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帮助我的是向数据数组添加第二个值-只有一个值不起作用。

当绘图仅包含一个数据点时，我使用PHP7.2时遇到了同样的问题。 原因似乎是JPGraph试图将单个数据点同时放在绘图的左边缘和右边缘

使用

$plot->SetCenter（）为我修复了这个问题，它在箱线图中看起来更好