I like to show mean lines on the 2d density histogram chart using Plotly.js. I saw that ggplot2 has the options to draw geom_vlines. For simple histograms, there are examples using layout, shapes. The shapes option seems to be a better choice. But I’m not clear on how to define the x0, y0, x1, y1 on the histogram subplots, xaxis2 and yaxis2.