Right now Power BI only supports render charts created by R visualization component as PNG.
Try the following:
p <- plot_ly(x = dataset$period, y = dataset$mean, name = "spline", line = list(shape = "spline"))
plotly_IMAGE(p, format = "png", out_file = "out.png")
I'm not very sure if this will work. Try and let me know!
Thank you