I am a newcomer to the plot_ly package and am trying to produce a time series line plot with two variables on the y axis.
In my dataframe 'baro' I have 'DateTime' variable in POSIXct format, and 'Pressure' and 'Temperature' in numeric format.
I am basing my code off the example given here: https://plot.ly/r/multiple-axes/
p <- plot_ly(baro)
add_trace(p, x = ~DateTime, y = ~Pressure, type = "scatter",
mode = "lines", name = "Pressure")
add_trace(p, x = ~DateTime, y = ~Temperature, type = "scatter",
mode = "lines", name = "Temperature", yaxis = "y2")
layout(p,
title = "Pressure & Temperature", yaxis2 = ay,
xaxis = list(title="x")
)
This outputs a set of axes labelled -1 to 6 on the x axis and -1 to 4 on the y axis with no data plotted.

dput(baro)in order for us to reproduce your problem.