knitr：在循环中调用ggplot2函数时，如果伴随某些其他绘图函数则不会绘制

I'm not sure if this is a true bug or I'm missing something, but here it goes. I have a ggplot function (plot_data) that I'd like to call in a loop. I've included the function in its own chunk. Calling the function works fine in a loop in case one (the chunk titled "works"), in this case the plot_data function is followed by a barplot. However, in the second case, the plot_data() function is followed by a heatmap in which case, but the heatmap, oddly, suppresses the plot_data function. This happens whether or not plot() or print() is called around the plot_data function.I'm not sure if this is a true bug or I'm missi