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[Mike]

Hi David,

I have a figure containing two plots, via split axes, each showing position vs time. A reviewer has asked for another variable (velocity vs time) to be superimposed on each. i.e. I need two panels, each with two y axes.

I've looked at the template example for plotting two y axes on one graph by using the "Join Y" option. That works fine for a single chart. But is it possible to have two charts, each with two y axes? When I try that with the "Join Y" button, all the variables get drawn within a single plot frame. Is it possible to somehow specify which graphs to combine via "Join Y"?

Or will I need to draw each "double Y axis" chart in a separate DataGraph file, and then arrange them next to each other in a third?

Regards,

Michael

[David]

In the original plot, are the x or y axis stacked?

If the x are stacked, i.e. side by side this should be automatic. If they are one of top of the other, this is not currently easy in a single DataGraph file. You can do it using an extra axis but it is somewhat of a workaround.

David

[Mike]

They are stacked: two graphs side by side.

But because of the way the data is plotted, what I actually want is a double x axis rather than double y (I just described it as double y because that's the normal terminology).

Does that make a difference?

[David]

So you mean that you want a left and right graph, and on both graphs you have two x axes.

Right now you would have to use a similar trick as is used in this template. It is for the y axes.

David

[Mike]

[Mike]

Hi, finally got a chance to replicate the example. I can get multiple data series on each of the two plots, by making a scaled version of one variable so that it can be plotted on the range of the other.

The variables have quite different ranges (one ranges from -40deg to +20deg, the other from -500deg/s to +500deg/s), so I have to scale the second by about 0.06 in order to plot it on the same axis as the first. So that works OK. But my question is how do I get the axis at the other end to reflect the original data range?
I can't quite work this out from the example template. There is an option on the axis to "Convert units", with "data" specified as "c" and "Display" as "10". I'm not sure what either of those mean: the tooltips aren't clear to me, and the relevant diagram in the help seems to have different labels ("units" and "data units") so I'm not sure if it is doing the same thing?

[David]

I changed the tool tip to the following:

[Mike]

I'm scaling completely different variables (position and velocity) so I can't use any of the inbuilt unit conversions. Is there a simple way to scale the tick marks on an axis to match an arbitrary conversion factor?

e.g. I scale my velocity values by 0.06 so that they can plotted on the same chart as the position values. But then I need tick marks on an axis which reflect the actual velocity values.

I've put "1" in the "data" box and "0.06" in the "display" box. That seems to produce axis tick marks which are approximately correct but it is hard to know if I'm doing the right thing...

[David]

That should work. The ratio is all that matters, so 2 in both will not cause any changes.

The only restrictions for now is that it needs to be a scale. For a scale + shift, the only thing I support at this point is temperature conversion.

If it looks right, it should be exactly right. Either the scale is 1/0.06 or 0.06. Unless you are doing a conversion like 1/0.94 you should see it. You can use the context menu to see the coordinate (of the click). Or the loupe tool to see if the conversion looks about right.

David

[Mike]

Many thanks.