Gnuplot in shell. It's old and finicky, but it works and whatever you want to do, someone has done it before and written it up. Those instructions from 15 years ago will still more or less work as well. I output to SVG as part of website stats tools sometimes, which is handy.
For web I like plotly. Usually I will use the UI tool to make a chart I like, and then just automate the data portion. Same for highcharts. Those UI plot makers are fantastic if you just want to template something.
For web I like plotly. Usually I will use the UI tool to make a chart I like, and then just automate the data portion. Same for highcharts. Those UI plot makers are fantastic if you just want to template something.