Agreed (except about the “this is fine” part). The arguments are unconvincing and the recommendations seem bad. (In particular, the suggestion that the “vary between $50T and $53T” graph shouldn’t be drawn with a zero-based y-axis is egregious.)
If I measure gravitational force against altitude, and end up with points like the following:
0 ft above sea level, force is 9.8000 m/s2
1000 ft above sea level, force is 9.7992 m/s2
2000 ft above sea level, force is 9.7986 m/s2
3000 ft above sea level, force is 9.7980 m/s2
would it be egregious for me to plot this graph without a zero-based y-axis? Do I need to plot it with a y-axis going down to zero?
Certainly there are cases where it’s misleading to not extend a graph like this down to zero. But there are also cases where it’s entirely reasonable to not extend it down to zero.
I’m surprised to hear you say that. I would consider it perfectly reasonable to use a line graph without a zero-based y-axis to plot gravity against altitude: the underlying reality is in fact a line (well, a curve I guess)! Gravitational force goes down with altitude in a known way! But the effects of altitude on gravity are very small for altitudes we can easily measure, and extending the graph all the way down to zero will make it impossible to see them.
Eh, I’ve encountered plenty of times when I really needed to understand the variance of data such that I had to “zoom in” and put the start of the axis at something above 0 because otherwise I couldn’t find out what I needed to know to make a decision. But I do often like to see it both ways, so I can understand it both in relative and absolute terms.
Just so; the correct way is indeed to show the full (zero-based y-axis) chart, then a “zoomed-in” version, with the y-axis mapping clearly indicated. Of course, this takes more effort than just including the one chart; but this is not surprising—doing things correctly often takes more effort than doing things incorrectly!
Agreed (except about the “this is fine” part). The arguments are unconvincing and the recommendations seem bad. (In particular, the suggestion that the “vary between $50T and $53T” graph shouldn’t be drawn with a zero-based y-axis is egregious.)
If I measure gravitational force against altitude, and end up with points like the following:
0 ft above sea level, force is 9.8000 m/s2
1000 ft above sea level, force is 9.7992 m/s2
2000 ft above sea level, force is 9.7986 m/s2
3000 ft above sea level, force is 9.7980 m/s2
would it be egregious for me to plot this graph without a zero-based y-axis? Do I need to plot it with a y-axis going down to zero?
Certainly there are cases where it’s misleading to not extend a graph like this down to zero. But there are also cases where it’s entirely reasonable to not extend it down to zero.
Would you graph with a line chart? No. And it absolutely would be egregious to use a line chart and then not use a zero-based y-axis.
I’m surprised to hear you say that. I would consider it perfectly reasonable to use a line graph without a zero-based y-axis to plot gravity against altitude: the underlying reality is in fact a line (well, a curve I guess)! Gravitational force goes down with altitude in a known way! But the effects of altitude on gravity are very small for altitudes we can easily measure, and extending the graph all the way down to zero will make it impossible to see them.
Here, I’d plot difference from gravitation at sea level.
Eh, I’ve encountered plenty of times when I really needed to understand the variance of data such that I had to “zoom in” and put the start of the axis at something above 0 because otherwise I couldn’t find out what I needed to know to make a decision. But I do often like to see it both ways, so I can understand it both in relative and absolute terms.
Just so; the correct way is indeed to show the full (zero-based y-axis) chart, then a “zoomed-in” version, with the y-axis mapping clearly indicated. Of course, this takes more effort than just including the one chart; but this is not surprising—doing things correctly often takes more effort than doing things incorrectly!